Would a Forgotten Realms Campaign Setting Book Make Sense?

 Ok, so the obvious response to my title is: "um, what about Sword Coast Adventurer's Guide?" And that's fair.

SCAG was the first 5th Edition book that was primarily built around detailing a setting, giving us some information about such famed places as Waterdeep, Baldur's Gate, Neverwinter, Candlekeep, and Daggerford, and the general Sword Coast region of the Forgotten Realms, which is the sort of basic "home base" region of D&D's default setting.

The published adventures, with a couple exceptions, are set on the Sword Coast (even Out of the Abyss is, I believe, set in the Underdark regions below the Sword Coast.)

But SCAG is also generally derided as one of the most unnecessary books in the 5th Edition collection. It's very thin, and while it comes with a bunch of playable subclasses, only two or three of them are actually considered any good (indeed, a lot of the debate over the Undead patron that appeared in Unearthed Arcana has been about how it steps on the toes of the Undying patron - to which I say "good! Let this be a much cooler replacement!")

Since SCAG, we've had four campaign setting books with Guildmaster's Guide to Ravnica, Eberron: Rising from the Last War, Explorer's Guide to Wildemount, and Mythic Odysseys of Theros. Each of these has, I think, been received with a lot more enthusiasm.

So there is something to be said that WotC might have learned a lot on how to make these books more interesting and useful to DMs and players, and while the Core Books provide content that's perfectly suited for the Forgotten Realms, the books don't provide the extensive geographical detail you get in a dedicated setting book.

On the other hand, we've also gotten quite a bit of info for these locations in some of the published adventures. Waterdeep: Dragon Heist and Baldur's Gate: Descent into Avernus both have extensive "gazeteers" that provide a lot of info on their urban settings. Icewind Dale: Rime of the Frostmaiden doesn't have the same sort of segment, but that location's more focused on the barren, frozen wastes, and we get a bit about Ten Towns.

The existing campaign setting books tend to focus on particular regions in their settings. Eberron gives us mostly info about the continent of Khorvaire, though there's a bit of info on Eberron's planes and some of the other continents. The Wildemount book of course only tells us about the eponymous continent in Exandria, with not a lot about Tal'dorei or other parts (though given that there was a separate, independent publication for the Tal'dorei setting, it could be seen as redundant.)

Actually, the previous parenthetical is the real issue here: wouldn't an FR setting book be kind of redundant? We know a ton about the Forgotten Realms already. And between all the published adventures, I think it would be easy for DMs to come up with their own adventures set there.

That being said, there's a Magic the Gathering set coming out next year set in the Forgotten Realms, and the previous crossovers have come with the release of Magic sets based in those worlds - the 2018/2019 "season" was all set in Ravnica, while 2019/2020's middle non-Core Set release was Theros Beyond Death. So I wouldn't be shocked if one of the three campaign setting books that come out will be FR-based - though I'd hope it would focus on the larger world, giving us other parts of Faerun and even the other continents (none of which I could name if you held a gun to my head.)