The Siege of Undercity and the Burning of Teldrassil

Somewhere in the storm of information yesterday, I heard that Battle for Azeroth's cinematic, in which we see an epic confrontation between the Alliance and the Horde (notice that both sides have a "darkest hour" moment and then are rallied by their faction's leader?) will function similarly to that of Legion - a sort of prologue bit that feeds directly into the intro event. That suggests that the Siege of the Undercity is going to probably be a massive scenario like the Broken Shore.

We know the aftermath of that event - the Horde is forced to flee from the Undercity, and the Alliance destroys it, taking Lordaeron.

But we also know that Teldrassil will burn, and the Horde captures northern Kalimdor, establishing the two continents as truly "the Horde one" and "the Alliance one."

Presumably it is within this context that we'll be going to Kul Tiras and Zandalar.

While I imagine Undercity will be experienced in-game (maybe making up for the fact that post-Cataclysm no one can do the Battle of Undercity quests from Wrath,) I don't know what goes on with Teldrassil.

I suspect that narratively, the burning of Teldrassil might be misdirection. While the Horde is clearly set up to conquer Kalimdor, such an event could be what spurs the Alliance to invade Lordaeron. Indeed, I suspect that this siege is where the war proper kicks off.

So what if Teldrassil wasn't actually burned by the Horde?

While tensions between the factions are always high, the fact is that we're going to need some external threat for a final boss to the expansion, and barring a return to Warcraft 1-style "different canon depending on which side you play" storytelling (the chance of such happening being about zero) we're going to need someone outside of the Alliance and Horde to fight. I doubt we'll take down Sylvanas, as we've already done the "Horde Warchief goes too crazy with the war and needs to be taken down by rebels within and Alliance without." Theoretically we could do so with the Alliance, perhaps ending with a "Siege of Stormwind," but that's not too much better.

I'm still putting some money on N'zoth being behind this, especially as there are hints of Old God stuff on both islands. And given that this is the South Seas expansion we've always suspected was coming, it makes sense that we would face the God of the Deeps. Hell, we're getting Azshara this time, so we know that some major external threats are at work.

So a narrative that makes a ton of sense to me is if N'zoth's cultists or the Naga were the ones to burn Teldrassil and frame the Horde to make it look like it was them. Then the Alliance marches on Undercity to "end" the Horde just as Varian promised at the end of Siege of Orgrimmar, and by the time anyone finds out the Horde didn't light the fire, the war's already raging and impossible to stop.