100 acre wood- while it started as a nostalgic take on a series one loved by all, the mini game based progression has been done enough throughout most of the games so i would be surprised if they did bring it back again in KH3
Atlantica- While i do think Atlantica in kh1 is good conceptually and was even pretty advanced for squaresofts (at the time) current graphics/hardware engines, the world has been quite overdone and the kh2 version totally killed most of the fan reception of the world. Woudl rather pass on it even though it would be great seeing an underwater world with the Unreal engine 4 that KH3 and birth by sleep 0.2 will use.
Musicals, lets just not