The roster situation for KOF15 will be very interesting to see. If we get a visual style that looks similar to a ASW fighting game, then I think we won't get much more than 30 characters on launch. Which--I can think of around ten teams that are nigh guaranteed to be in the game, which leaves out a LOT of characters from XIV.
Japan Team
Yagami Team
K' Team
China Team
Fatal Fury Team
Art of Fighting Team
Ikari Warriors Team
Psycho Soldier Team
Women Fighters Team
These teams I think are guaranteed to be in the game, with the China Team being the only XIV Team to return. Now, you can always tweak the actual teams themselves, so that some characters return and some don't--like, maybe Mian is in the China Team and Tung is not. That said, it does limit the potential teams we could see if that's the route we see KOF15 go.
Krispykaiser said that Tung has never really been all that popular and is one of the least popular characters in XIV according to their data. Wouldn't be surprised if he's out.
He also said that Xanadu is very unpopular as well (even though SNK themselves really like him).
XV is very interesting in that we can expect a smaller cast than XIV but at the same time the potential for the cast is through the roof.
The story for XIV makes it so that any character can be brought back from any time or game (even from a non-SNK game) so it would be a real shame if they just wasted that on the launch roster mostly being just KOF regulars.
They should also be heavily considering having teams from Tekken etc. like in KOF All Stars. Gender bending EX versions of characters would be a fun addition too.
And at the same time I can't see them not including Mian and Nelson's teams since they are part of the story. Not to mention Ash was brought back to life. Luong ended up really popular as well.
So yeah, lots of potential and question marks when it comes to the roster. As always, they have too damn many good characters.