So, my wanted stages for the WiiU version. I assume they're going to be more than the 3DS one, AT LEAST 50. I'm also assuming the leak roster is the final one and we're not getting more than that. There are definitely too many but this list would be sheer perfection for me.
Mario:
- Mario Galaxy
- Mushroom Kingdom U
- Bowser's Castle (Mario Kart 8, works in a similar way to Mario Circuit but has also fire/lava hazards)
- Melee's Rainbow Cruise
- Brawl's Delfino Island
- Treacherous Tower (from Luigi's Mansion 2, may be a vertical stage)
- Paper Mario (same as 3DS)
Donkey Kong:
- Donkey Kong Island (Tropical Freeze, transformation stage, starts normal and then gets freezed)
- Brawl's 75m (reworked to be a lot better)
Yoshi:
- Yoshi's New Island (very similar to previous Yoshi stages, fairly basic)
- Yoshi's Woolly World (moving stage, preview of the game)
Wario:
- Wario-Ware 2 (works exactly like the first but with new minigames)
The Legend Of Zelda:
- Skyloft
- Desert Palace (from A Link To The Past, large stage like Coliseum)
- Gerudo Valley (same as 3DS)
- Brawl's Pirate Ship (the same but the weather changes like in Wind Waker)
Kirby:
- Lor Starcutter (from Epic Yarn, moving stage)
- Brawl's Halberd
- Melee's Green Greens
StarFox:
- Lylat System (the one shown, works like always but moves to many, many different planets in a random way)
- Brawl's Lylat Cruise
F-Zero:
- Melee's Big Blue
- Brawl's Port Town Aero Dive
Metroid:
- Pyrosphere
- Meridia (from Super Metroid, has water hazards and various enemies that may appear)
- Brawl's Frigate Orpheon
Pokémon:
- Pokémon Stadium 3 (fairy, dragon, poison, bug)
- Poké Floats 2 (updated with new Pokémons)
- Kalos Pokémon League
- N64's Saffron City (exactly the same, with just Gen I pokémons appearing)
Fire Emblem:
- Coliseum
- Brawl's Castle Siege
Earthbound:
- Threed (I just like how it looks honestly)
- Melee's Fourside
Kid Icarus:
- Palutena's Temple
- Reset Bomb Forest (same as 3DS)
Pikmin:
- Garden Of Hope
Animal Crossing:
- Town And City
Wii Fit:
- Wii Fit Studio
Punch-Out!:
- Boxing Ring
Xenoblade:
- Gaur Plain
- Eryth Sea (similar to Halberd, cruise stage)
Pilotwings:
- Pilotwings
Retro:
- Balloon Fight (same as 3DS)
- Open Field (from Duck Hunt, the Hunter is an hazard)
- Gyromite (R.O.B.'s stage, the doctor moves around the stage and the pillars are hazards)
- Mountain 1 (Ice Climber stage, vertical one done in retro style)
- Brawl's Flat Zone 2
- Dr. Mario (yes, it's placed in the Tetris-like place of the game, and you have to avoid viruses)
Third party:
- Pac-Land
- Dr. Wily's Castle
- Windy Hill Zone
- Brawl's Green Hill Zone
Smash Bros.:
- Battlefield
- Final Destination
- NintendoLand (yep, Mii's stage)
In total, 56 stages, with a lot of them being either returning ones or shared with the 3DS version. That seems absolutely doable to me, but we'll see. I just hope the stage selection for the WiiU version is better than the 3DS one.