DLC?
Sora, a new Pokémon, character from that phone game, Bandana Waddle Dee and Banjo-Kazooie.
Ideal DLC?
Ninten, A Tekken rep, Old Isaac/Matthew (for the Golden Sun fans), Banjo-Kazooie and Geno.
If Geno is deconfirmed by being a Spirit, then replace him with Shantae, Rayman or Crash, and have Banjo-Kazooie be the final reveal.
I do feel like Geno would be a great first reveal for the next game, though, the same way Ridley was for this one. If he actually does get in the next game, Ridley and King K. Rool would have to return, I think! Have the trio all together.