Good topic.
I agree that Toon Studio needs an overhaul. Especially now there's Remyland right next to it, its like night and day of theming. They will probably increase the Pixar presence there, but even though I've criticised Toon Studio I think there are plenty of other lands that need attention first.
The Back Lot is still a swathe of concrete that reminds us of the disappointment of '02. There was talk of additional themeing around there, which I could see happening (its a relatively cheap and quite way to spruce up an area).
The Fantastic Four aren't going to be replacing Armageddon Effets Speciuex any time soon, but I doubt that would have any major impact on any proprosed rethemes in that area. That means that AES will probably stay around for the near future, unless they did have a back up plan.
After that, the really need too look at building a proper Hollywood Blvd., but whether that comes before or after park expansion is anyones guess.
I can see them adding something beyond the berm - in the area behind Motuers (and you'd access the land between Mouteurs and RnRc). As to what that will be, well I guess its likely to be something Marvel. They could use Star Wars, but that seems more likely to be in Discoveryland now.
Once that area is reclaimed, then they can start looking at further additions outside the berm, but then we're looking into the '20s and its hard to say what they will do. Who knows, maybe they will add Star Wars Land to WDS and save Disco-land from a rather jarring thematic clash.
However, that hinges on what happens in the next half-decade. If they make some solid additions (just like they did with Remy) then this sort of expansion becomes more possible than it ever has been in the past.
