My thoughts:
First up, stages we know are 99.9% likely to be legal:
Starters:
Battlefield
Smashville
Town & City
Starters/Counterpicks:
Final Destination
Halberd
Lylat Cruise
Castle Siege
Counterpicks/Banned: Should these familiar stages be banned?
Delfino Plaza
Norfair
Port Town Aero Dive
Pokémon Stadium 2
Luigi's Mansion
Congo Jungle
New stage discussion:
Possible Starters/Counterpicks:
[Wuhu Island:](
https://www.youtube.com/watch?v=aggC4joE2wU) This stage is interesting, like many other moving stages, this level's stops appear to be completely random, possibly detracting from it's legality. Possible all of the different stops can be seen [here](
http://www.ssbwiki.com/Wuhu_Island). Out of the 8 parts we've seen, 4 of them appear to have walk-offs and many others have swimming if knocked into the water. The stage's moving sections appear to be completely random, however, they seem perfectly fine regardless. I am personally leaning towards counterpick on this one.
[Orbital Gate Assault:](
https://www.youtube.com/watch?v=sDw9iImsIok) At first glance, this may seem like an obvious ban, but here me out, I actually think it could be legal. There are indeed hazards on this stage, but they seem minor and predictable ala Halberd and Lylat Cruise, and shouldn't detract from any skill based fight. The stage isn't a scroller stage as it appeared to be either, and each of the different sections seem like they'd make fine stages on their own. This is one we'll obviously need more time with, but for now, I think it shouldn't be brushed off.
[Mario Circuit](
https://www.youtube.com/watch?v=31-W0hpJjWM): Another one that might be brushed off, but hear me out. This is yet another moving stages and it's stops appear to be completely random once more. Out of the four sections we've seen, one has a wall and another a single walk-off section. However, the only two (one not in the video can be seen [here](
http://www.ssbwiki.com/images/8/86/SSB4_-_Mario_Circuit_Image_2.PNG)) appear to be completely legal. The racers this time around don't appear to interfere as much as with previous Mario Kart stages, and if it's anything like Rainbow Road, they could possibly be shut off. This is another one we need time with, but I am currently advocating for it's legality.
[Wooly World](
https://www.youtube.com/watch?v=N9RmAFOZD2U): Man, this stage is so cute, and hopefully it's yet another beautiful legal Yoshi stage! We've seen three areas of this transforming stage, and too of which are walk-offs, and pretty big at that. The platform arrangement is unique, and obviously one we'll need time with, but let's not dismiss it just yet. I think if it's not legal for singles, it could possibly be a doubles stage.
[Windy Hill](
https://www.youtube.com/watch?v=p2q1Mgmkd04): This is a pretty big stage and the bumpers may detract from it, but I think we got a solid legal doubles stage on our hands if the bumpers and windmill don't turn out to be a big deal.
[Miiverse](
http://www.ssbwiki.com/Miiverse_(stage)): Battlefield clone apparently, but if the blast zones are different it might be worth using both.
[Skyloft](
http://www.ssbwiki.com/Skyloft): This stage's fate kind of rests upon whether or not Delfino should be banned, both very similar stages with some good sections and not-so good sections.
[Big Battlefield](
http://www.ssbwiki.com/Big_Battlefield): Probably not a legal singles stage, but definitely legal for doubles, 3v3s, and 4v4s.
Banned:
Pyrosphere: Could have been an awesome legal stage if it weren't for the space dragon and exclusive-items showing up.
Kalos Pokémon League: I think this could have been a counterpick if it weren't for Rayquaza crashing the party.
Gamer: Awesome layout, too bad about 5-Volt.
Mario Galaxy: Weird gravity and constant walk-off, maybe a counter-pick if walk-offs aren't as big a deal though.
Mushroom Kingdom U: I think it's still possible to be a counter-pick, but leaning towards ban because of Nabbit moreso than Kamek.
Wii Fit Studio: Possibly legal if walk-offs aren't a big deal anymore.
Everything Else: Hazards, walk-offs, and scrolling galore!