There's room for a resort:
1. In between the TTC and Contemporary
2. North of the Grand Floridian, in between Floridian Way and the canal to the west of MK
3. North of the Contemporary (in addition to building DVC to replace the convention center or garden wing, which I wouldn't consider a new hotel)
4. In between Wilderness Lodge and Fort Wilderness on Bay Lake (technically this would be classified as an "MK area" resort)
It could be that each of these areas aren't very suitable to build on, but the location is so prime that eventually it will be worth it to
make them suitable. It could be dozens of years away, but I'd bet that all of those locations are built on at some point. We know that they have had some level of planning for spots 1 and 4 at least in the past.
As far as behind MK, I feel like eventually they are going to expand MK out around the Rivers of America like they are currently doing with Star Wars Land at
Disneyland. I don't see them ever putting hotels back there because it limits the best area they have for expansion.