Seeing how I don't have Melee, I would of loved if Flat Zone 1 was the stage for Mr. Game and Watch and not Brawl since I have Brawl, however It's possible that more DLC stages will come after the Miiverse stage, I'm hoping for...
Flat Zone 3
Magicant
Mute City
And maybe a R.O.B stage? But I have a feeling they'll treat Wrecking Crew stage as the R.O.B Stage like the Mario Bros. Stage from Brawl.
And It would be really weird if Congo Jungle 64 is the only 64 returning stage, if they only had to limit it to the 64 Melee stages, then I expect Yoshi's Island 64 and Dream Land 64 to come back.