Probably the last time I do this, but a sort of prediction image regarding Wii U stages:
Left to right, unconfirmed denoted by asterisk--
Battlefield
Final Destination
Mario Galaxy
Mushroom Kingdom U
Luigi Circuit*
Bowser's Castle*
Rainbow Cruise (Melee)*
Nep-Enut's Domain*
Wonky Waterway*
Skyloft
Pirate Ship HD*
Temple (Melee)*
Pyrosphere
Frigate Orpheon (Brawl)*
Great Cave Offensive
Halberd (Brawl)
Orbital Gate
Lylat Cruise (Brawl)*
Royal Unova*
Kalos Pokemon League
Pokemon Stadium 2 (Brawl)*
Port Town Aero Dive (Brawl)*
Coliseum
Castle Siege (Brawl)
Onett (Melee)
Palutena's Temple
Gamer
Garden of Hope
Town & City
Smashville (Brawl)
Wii Sports Resort*
Pilotwings
Wii Fit Studio
Boxing Ring
Gaur Plain
Flat Zone 3*
75m (Brawl)*
Wrecking Crew*
Miiverse*
Windy Hill
Wily Castle
Pac-Land
Seeing them together like this I'm starting to doubt that past stages will be mixed in together with the new stages in the Wii U version like they are in the 3DS version, if only because Town & City sitting right next to Smashville looks absurd. But whatever.
Some quick thoughts on the unconfirmed ones I used:
Luigi Circuit: No way are we done with Mario stages, and Mario Kart is such a big part of Mario nowadays that I don't see it getting skipped up. Mario Kart Wii especially was
such a huge game that I think a stage from it is a given, and I anticipate the Wii U version getting a more "regular" Mario Kart type stage to contrast Rainbow Road in the 3DS version.
Bowser's Castle: This is intended to be a retro Mushroom Kingdom esque stage. It seems like an unwritten rule that ever Smash has to have a stage based on the original Super Mario Bros., explaining Mushroomy Kingdom in the 3DS version. Struggled to come up with a type of stage that hasn't been done before though, so maybe they could do a castle type stage? I dunno.
Rainbow Cruise: If only because its music is available in the 3DS version for Smash Run. I dunno.
Nep-Enut's Domain: Probably would just be called Yoshi's Island if we want to be honest. I don't have much thought here other than I think the Nep-Enut (big blue guy) is pretty emblematic of Yoshi's Island and while I think there will be a new Yoshi stage in the Wii U version I have hard time thinking of what it could be.
Wonky Waterway: The big sprawling background jungle vistas I think are DKCR's most well known visual feature, and the temple with the retro Donkey Kong statue may be the most iconic. Seems like a likely choice to me even, but what do I know.
Pirate Ship HD: I was thinking along the lines of "Pirate Ship 2," just used a picture from TWWHD to help visualize it. I'm thinking same basic layout as Pirate Ship from Brawl, but with The Wind Waker HD's visual look to it and with new hazards.
Temple: It's music is in the 3DS version for Smash Run and it's just too popular to be left out I think.
The quintessential Melee stage in the eyes of many.
Frigate Orpheon: Just thinking they may choose to throw the Prime games a stage bone with a past stage at best.
Lylat Cruise: The voice credits for the Star Fox codec calls from this stage are in the 3DS version, and I'm thinking it has something to do with being able to use the 3DS as a controller for the Wii U version.
Royal Unova: I was thinking maybe a second new Pokemon stage could be a city from Black & White, to contrast the 3DS's version--a city for one generation, a league for another. The Royal Unova could sail around the city like it does, under the bridge, offering views of Castelia city at night and whatever.
Pokemon Stadium 2: I'm anticipating that most veteran franchises will get past stages, especially the bigger ones, and Spear Pillar is out of the question due to Palkia being a Poke Ball Pokemon. Maybe this could be the original Melee Pokemon Stadium instead. Not married to the idea.
Port Town Aero Dive: It's unfortunate, but I'm thinking Magicant and Mute City are 3DS exclusive and that Mother and F-Zero are the odd ones out in the Wii U version in terms of stage representation. Port Town would be the best representative for F-Zero then.
Wii Sports Resort: I dunno what to call it, but set on the platform where swordplay duels are set. Wii Sports Resort is one of the unaccounted for franchises listed in the 3DS version's data (which also includes the Wii U exclusive Pilotwings), so there's probably a stage from it (assuming it wasn't cut), but it does seem odd to have two stages set on Wuhu Island. Though maybe that's in character for Wuhu Island?
Flat Zone 3: Just used Greenhouse to represent it because I got the idea from the Tower of Smash bs. I think a new Game & Watch stage is essentially guaranteed due to it lacking one in the 3DS version (and I don't see there being zero new G&W stages between both versions), so Flat Zone 3 seems likely...
75m: I don't like this stage at all, but I think it may be that retro representation is more important than whatever Rumble Falls is, though I guess Rumble Falls' Stickerbrush Symphony is in Smash Run... I dunno. I could go both ways here. 75m or Rumble Falls.
Wrecking Crew: Another unaccounted for franchise in the 3DS version's data. Seems self explanatory.
Miiverse: The third and final unaccounted for franchise in the 3DS version's data. Didn't know how to visualize this in a picture form, but I'm thinking the stage could be something like Pictochat, maybe?
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That's all I got. I am afraid that this is still way too optimistic.