There will be more newcomers announced other than the ones in the Gematsu leak

[New Super Mario]

So this is my theory. A lot of people are just saying the gematsu leak it true and that they will be the newcomers.

But I still think there will be a few more (maybe 2 or so).

Because, if you think about it, we have Rosalina. Rosalina was NEVER mentioned in the leak and was revealed before characters like Palutena, Pac-man, and the Miis.

This leads me to believe that we could expect a few more newcomers, perhaps from Zelda (Ghirahim!) or Metroid (Ridley), or just something random.

 

[GalacticPetey]

The common theory is that the Gematsu leaker has something to do with marketing or is involved with E3 in some way. That's why he had access to what characters they were gonna show. It's safe to assume that the characters he mentioned were all planned to be shown at the two E3s, but whoever was in charge changed their mind and revealed other characters at different dates.

His information is also likely old and a little outdated (hence the "Pokemon from X and Y" quote as opposed to just Greninja. Sakurai did confirm they had a roster slot for a pokemon from X and Y and decided on Greninja a little later).