Why would you think that they've decided what's happened to any part of the forgotten realms that they haven't already published in a book? Maybe they want to leave it open so that they can decide what happened to suit a future story. Maybe they'll decide that some place or another has been occupied by some organization/species/outer plane for several years since they detailed it, but if they write a campaign setting that details it, they won't be able to do so? It gives them the luxury of leaving everything in the box with schrodinger's cat until they decide to what it needs to have been.
Maybe they'll leave FG semi-static for a while and redevelop areas of it in the TableTop RPG as they write adventure paths and dedicate Dragonlance or Greyhawk to ongoing metaplot - movies, novels, comic books.
Yeah, I get that a blank sheet is a wonderful thing which contains all the possibilities of the future, but now, it's a boring blank sheet.
Remember the 5E design philosophy about not repeating past formulas? For example, instead of Monster Manual II, we got Volo's Guide.
Well, instead of a Forgotten Realms Campaign Setting, we got the Sword Coast Adventurer's Guide. That is the 5E FRCS. They're not going to do another one any time soon.
Why would you think that they've decided what's happened to any part of the forgotten realms that they haven't already published in a book? Maybe they want to leave it open so that they can decide what happened to suit a future story. Maybe they'll decide that some place or another has been occupied by some organization/species/outer plane for several years since they detailed it, but if they write a campaign setting that details it, they won't be able to do so? It gives them the luxury of leaving everything in the box with schrodinger's cat until they decide to what it needs to have been.
There was nothing to stop them from defining, say, the Underdark with Menzoberranzan etc and then turn around and have the Out of the Abyss story line, or Waterdeep and the Sword Coast and then have a Cloud Giant City turn up in Storm King. It is just not as Schrodinger as you may think.
So you're saying that if they need a city to have been occupied by an army for 5 years, they should just retcon it and invalidate a FRCS that had been written before they worked out the storyline?
No, I am saying that because there is no timeline on their adventures as in it must happen in the year of the Fruitbat, then they can just write in the adventure that the army has turned up for 5 years.