Blizzard is doing something a little on the risky side by having back-to-back expansions exploring existing, established parts of the world. Truly, there's no direct precedence here, though Warlords of Draenor (hardly a model for expansions that Blizzard would want to follow) did give us the alternate timeline/past version of many places we visited in Burning Crusade.
While Draenor was an alternate timeline, we can probably assume that this is what Outland looked like prior to the degradation of the planet at the hands of Fel magic and eventually its shattering from Ner'zhul's overzealous portal creation.
Midnight took advantage of the fact that Quel'thalas, then Eversong Woods, the Ghostlands, and The Isle of Quel'danas, were stowed away in a separate instance than the rest of the Eastern Kingdoms to simply place the modern, updated one into an updated Eastern Kingdoms map (allowing access to the old one via portals).
All in all, while Quel'thalas did exist in Burning Crusade, only three of its zones were directly translated into the Midnight versions, merging Eversong and Ghostlands thanks to the healing that has occurred (beyond the Ruins of Deatholme, the actual border between the two BC zones is far from obvious in the updated version). While the raid, later converted into a dungeon during Cataclysm, was called Zul'Aman, that has been kind of retconned into saying that what we were fighting through was actually Atal'Aman, the temple city at the center of the zone, which has been pretty faithfully recreated as part of that zone, but with the rest expanded out to give us a more conventionally sized WoW zone that was always implied to be there.
Midnight then has places like Harandar, Voidstorm, and the Coiled Isle, all of which are pretty much new to the lore of the game (while it was established that Mythrax was buried somewhere in Zul'Aman, I had previously assumed it was under Atal'Aman).
We don't really know precisely how The Last Titan will approach a return to Northrend. Unlike Quel'thalas, which was just a pair of starting zones for Blood Elf characters and then, at the end of the expansion, the setting for the final raid (I don't think Warcraft III ever implied that the Sunwell was on an island north of the capital,) Northrend was a full continent that we really spent basically all of Wrath on (if memory serves, the only things Wrath brought to the old world were Stormwind Harbor and the eastern coast of the Eastern Plaguelands, to serve as the area for the Death Knight starting experience).
When first announced way back in like 2023, back when the World Soul Saga was first revealed, there was mention of the expansion being centered around Ulduar.
Now, Midnight has done something interesting by not actually giving us a new "continent" but instead just expanding one of WoW's original continents (and then also adding two zones that are disconnected from any continent, which I'm assuming will also be the case for 12.2's zone). It's funny, actually, that at this point I think the subcontinent of Lordaeron is larger than the southern part of the Eastern Kingdoms (the Khaz Modan/Stormwind/Zul'Gurub part of it).
Thus, before we even get started: are we sure that Last Titan will even use all of Northrend?
I think it would be a little awkward not to: Quel'thalas was partitioned off from the rest of the Eastern Kingdoms (I think it was technically on the Outland map, along with Azuermyst and Bloodmyst Isles). But if Last Titan were to only, say, update Storm Peaks, Crystalsong, Dragonblight, and Icecrown, it would be unclear how that should work: shouldn't the 2008 version of Northrend just be left in one intact piece and the Last Titan version stand on its own as something totally new?
Now, Northrend was the setting for WoW's second expansion, and as the years have gone on, Blizzard has tended toward somewhat different standards for an expansion's zones. Northrend has ten zones (eleven if you count the tiny Hrothgar's Landing off the coast of Icecrown). Now sure, Crystalsong had very little actually in it (a few quests that were part of the Icecrown quest chains, but mostly just Dalaran floating above it) and Wintergrasp was a novel experiment in world PvP, which they kept tinkering with with Tol Barad and Ashran, though they seem to have kind of given up on such projects.
Still, even if we cut out those two, there were eight zones with pretty fully-fleshed out questing experiences.
In contrast, recent expansions tend to launch with four zones that you'll level up in. Other zones will be added, but these come in major patches - again, apart from Hrothgar's Landing (a tiny island with I think just like one Vrykul you had to kill for an Argent Tournament daily quest), Wrath never added any zones over its patches. The game was far less focused on outdoor content - while the Argent Tournament added a lot of daily quests in both 3.1 and 3.2 (I think in 3.0 it was just an open bit of snowy tundra, but they were starting to build it when Ulduar came out) there wasn't really any outdoor content added to the game outside of it, with the focus being far more on running dungeons and raids.
The formula today is generally that you get a reputation faction (or rather, a Renown faction) in each of the major zones, and the zones then scale up with you to the level cap, with max-level content there, and sometimes some additional repeatable stuff like the Void Incursions.
Basically, in the old days, a zone like Grizzly Hills was truly "used up" after you hit a certain level, and you wouldn't go back there unless you wanted to farm materials for crafting or if you were heading into a dungeon nearby (like Drak'tharon Keep).
Today, the emphasis is on bigger zones that you have lots of reason to return to over the course of the expansion.
Ok, so, what would a 2027 version of Northrend look like?
Well, I think if we're using the whole continent, even if modern zones are bigger, it's still probably a larger area than we tend to get in an expansion, at least at launch. Admittedly, my memory of is size is based on the old version of flying mounts, which were far slower than the post-Dragonflight skyriding system. (Also the improvements to draw distance do shrink distances - I remember being stunned at the fact that I could see Dalaran while I was down in Azsuna.)
But might we see zone consolidation, like how Eversong Woods absorbed the Ghostlands in Midnight?
I think that's likely to happen given the structure of modern WoW. But how do you justify it? The only zones I could really imagine merging from Wrath would be perhaps dividing Grizzly Hills and distributing part of it to Zul'Drak and part of it to Howling Fjord.
However, perhaps the teaser we got at Blizzcon hints at ways in which the continent might be changed far more than a simple graphical upgrade. That Titan construct, towering over Dragonblight and making both Wyrmrest Temple and Icecrown Citadel look tiny in comparison, would almost inevitably destroy much of what it walked through.
Thus, I could really imagine some massive destruction re-shaping the face of Northrend. Being just south of the Storm Peaks probably doesn't bode well for Zul'Drak (nor does the fact that we've already gotten a fair amount of Troll content in Midnight - though that doesn't guarantee that they'll skip out on it in Last Titan). The Drakkari Empire was in a pretty rotten state during Wrath, of course, and while they did have some representation in Zandalar, I could imagine things falling apart in Zul'Drak even before whatever wrathful Titan stuff is going on.
Now, I think one thing that will be interesting about our return to Northrend is that, while Icecrown Citadel loomed over Wrath of the Lich King as the very obvious final raid and headquarters of the expansions main villain (part of what made ICC and the fight with Arthas so memorable was that it was clear from the word go that everything was building to it throughout the expansion,) it's likely that the Scourge will be a secondary issue in the Last Titan. Might the Titans even go so far as to wreck Icecrown?
After all, the black ramparts of Icecrown were forged from Saronite, a pretty clearly non-Titan-approved building material (while they never really explicitly got into this, it seemed obliquely implied that the undead were immune to the maddening whispers of the Old Gods, which is potentially a really cool bit of cosmic rock-paper-scissors if they ever wanted to expand upon that).
I love the Scourge, but post-Arthas, and especially post-Shadowlands, it just doesn't seem like they can really be justified as a major threat in Azeroth anymore. While I'd frankly be offended if we didn't get any undead threats in Last Titan, I do think that it's highly likely that our main focus will be on the Titans and their constructs. Much as Ulduar was the mid-patch side story in Wrath, I expect that the Scourge/Icecrown/the Undead will at best be the mid-patch side story for Last Titan.
And if we've got Titan constructs rampaging across the continent with what I'm sure is a directive to "re-establish order" there, that gives them license to change a lot of things.
So, wild speculation time: let's go zone-by-zone.
Howling Fjord:
This was where we were first introduced to the Vrykul, which turned out to be pretty important as both the ancestors of humanity (and thus four of WoW's playable races) and also seemingly among the most common and widespread Titanforged races.
But the Vrykul of Howling Fjord are distinctly post-Curse-of-Flesh versions. They had also been in stasis for countless ages prior to the Scourge waking them up, so what do they look like A: after Ymiron died and B: potentially reconnected with other Vrukul cultures, such as the Stormheim Vrykul? (Also, can we confirm that the Drust were another group of Vrykul, and that the reason Kul Tirans are so burly is that they have far more recent Vrykul ancestry?)
Borean Tundra:
This zone had something of a less focused theme. The Coldarra is probably a more friendly place with Kalecgos in charge of the Blue Flight (also, it was something of a surprise that Malygos turned out to be a villain in Wrath, as he had previously been seen as a largely benevolent figure). Weirdly, the pretty huge notion of the Curse of Flesh was first introduced in just one of the major quest lines here.
Dragonblight:
I really think of this zone as being the heart of Northrend, and given its importance to dragons, it's a place we've revisited periodically, as swiftly as the Dragon Soul raid in Cataclysm, but also Wyrmrest Temple shares a fair bit of vibes with Valdrakken, and a newly-reunited draconic regime that is notably no longer loyal to the Titans feels like it could be a pretty major factor here. Add to that the likelihood that Iridikron is a major player in the Last Titan and even the fact that Vyranoth is the ice-based Primal Incarnate and you've got a lot of stuff to work with.
Also, how cool would it be if Naxxramas were crashed into the ground there after our victory against Kel'Thuzad back in the day?
Grizzly Hills:
Among the most beloved WoW zones, I think in large part due to the memorable fiddle music. I think that this zone is really what they were trying to recapture with the Azure Span in Dragonflight. The odd thing is that there... wasn't actually much that went on here. There were some quests involving the Worgen, back when Worgen were universally hostile monsters (I have a screenshot of an NPC who reveals the fact that the villagers are secretly lycanthropes demanding to know if my Worgen Warrior was bitten. I mean, duh, right? Back in Gilneas City). The fallen, failed World Tree of Vordrassil is here, and I believe is the tree that allowed the Old Gods to infect the Emerald Dream with the Nightmare, though that plot seems pretty much resolved, so I'm not sure what you do with it.
Zul'Drak:
As mentioned above, the Drakkari Trolls were in a rough spot. Not only were the lower parts of the zone taken by the Scourge, but the Trolls themselves had sacrificed their own Loa to gain power to fend off the Scourge.
If this place isn't in ruins, I think you have the potential to explore a civilization that has basically collapsed. The danger is that it might tread similar ground to what we got in Zul'Aman. Notably, back in Burning Crusade, it wasn't clear that the Amani had done anything out of step with their Loas' wishes (the bosses in that before Malacrass and Zul'jin were simply called "Nalorakk" and "Jan'Alai," etc., though later we discovered these were really troll priests who had stolen their Loas' essence).
Sholazar Basin:
The weird outlier zone, which I think was there in part just to give us a break from all the cold and ice. Not a ton actually happened here, though it's also deeply tied to the Titans and their experiments on Azeroth (more evidently Titanic in nature than its counterpart of Un'Goro Crater in Kalimdor).
Given that we now know that Life is a separate cosmic force from the Titans' Order, might we see some tension between the Titans and their attitudes, as hinted at in lore books we got in Dragonflight?
Crystalsong Forest:
A bizarre, small zone that I think mainly existed to have not a ton of stuff going on underneath Dalaran. Well, Dalaran sure isn't showing up in Northrend again, so what they actually do with this is up in the air. Night Elf ruins are not quite as prominent in Northrend as they are in other parts of the world, but we have a bit of those here.
Wintergrasp:
Does Blizzard want to actually re-create the game's first dedicated PvP zone as a PvP zone? The place is also a Titan facility, so outside of that specific gameplay purpose, it could have other functions. Fun fact, Vault of Archavon was where Wrath's equivalent of World Bosses was, which they tied to PvP for some bizarre reason, doing so again in Cataclysm with Tol Barad. Mists of Pandaria brought World Bosses back into the world, but way, way later in 12.1, we got Lairs, which seem to be once again throwing world bosses into instances. They probably want to vary it up, but I wouldn't be shocked to see the Vault of Archavon function as the Lair for the 13.0 world boss.
Storm Peaks:
Well, surely this is going to be the center of it all, right? With Ulduar as well as tons of other Titan facilities, this is going to be a very important location for the expansion, and I'd be shocked if the expansion's first raid weren't here (this is another example of how expansion design has shifted: back in the early days, you wouldn't expect to go into the big, scary, central-to-the-expansion's vibes structure until the end of the expansion, primarily with Black Temple and Icecrown Citadel. Catalcysm shifted things, with Bastion of Twilight being among the first raids, and since then, final raids have always shown up in new zones or repurposed old ones).
Icecrown:
Again, given the shift in emphasis, we're going to likely see Icecrown playing second-fiddle to Storm Peaks in contrast to how it was in Wrath. But this is still a storied location, home to some of the most beloved stories out of WoW (and also some controversial ones, like the entrance to the Shadowlands).
I was actually really excited when, at the end of Sepulcher of the First Ones, the Jailer activated the Soul Forges under ICC, which were established in the 3.3 dungeons as part of the Lich King's vast array of sinister-looking tools, but whose purpose was ambiguous.
Again, I don't know how much they want to really build out of the lore of Shadowlands given how unpopular it was (I will say that I actually found a lot to like in Shadowlands, but I think it fell short of its potential, not helped by both Covid and the breaking news of all the horrible scandals at Blizzard that had come to light,) but as the place most closely tied to another major cosmic force that contrasts with Order, I could imagine the Titans being none-too-pleased about this frozen land of the undead being so close to their central command station on Azeroth.
Even if the Last Titan doesn't focus on the Scourge or undead in general as much as Wrath did, I think it would be insane for us to come to Northrend and not at least touch on it. Icecrown is both less important with the end of the Lich King (not Bolvar individually, but the Helm of Domination) but also more important given its connection to the Shadowlands.
What the zone actually looks like? That I'm not sure about. All those Saronite ramparts would presumably be very difficult to actually destroy or dismantle, and there's a part of me that wonders if the resilience of the architecture there might actually wind up being an important asset in fending off the zealous Titanic enforcers.
Arthas is deader than dead, but the Scourge as a thing is notably still around, just leaderless and disorganized. Nowhere more appropriate to explore what that means than Icecrown.
Anyway, we're still surely many months away from learning about the Last Titan's features and general scope.
I will say that while I did technically start playing in Vanilla, and I was there for all of Burning Crusade, Wrath was the expansion that I first felt that I really experienced nearly in its entirety at the time. We didn't actually get the Lich King down, but this was the expansion in which I first found a guild that did regular raiding, and I felt like I was truly getting all I could out of the game.
So I am full of Northrend nostalgia. Curious to see what they do with it.