Well the new Star Fox stage isn't on the Great Fox and it enter's Coneria's atmosphere...
Since nobody else has yet and I'm also on the SSBB site...
CURRENT CONFIRMED STAGES:
Delfino Plaza (Super Mario Sunshine)
Yoshi's Island (Um...Yoshi's Island? =P)
Lylat Cruise (Starfox)
Bridge of Eldin (LoZ:TP)
Smashville (Animal Crossing)
As for what I'd like to see return, the unlockable Mario stage in SSB64 was the awesomeness xD
And I also liked how each character had a special entrance based on the game they're from =P