If Geno got in as playable, that would shock me because it would run so contrary to every other character who's been in SSB, SSBM, or what we've seen so far from SSBB. We've only ever gotten...
Main characters from main franchises: Mario, Luigi, Bowser, Peach, Yoshi, Donkey Kong, Ganondorf, Fox, Kirby, Samus, Zelda (+ Sheik), Link, Young Link, Pikachu, Jigglypuff, Mewtwo, Zero Suit Samus, Ike, Pokemon Trainer, Meta Knight, Snake
Main characters from secondary franchises (not referring to quality, but sales): Captain Falcon, Ness, Ice Climbers, Mr. Game & Watch, Marth, Roy, Pit, Wario, Diddy Kong
Secondary characters from main franchises: Pichu, Falco
Geno is a secondary character from a secondary franchise, and I expect him about as much as other secondary characters from a secondary franchise, like Daisy or Waluigi. (Even though I'd really appreciate Daisy.) The only thing I see keeping his chances for being in even slightly alive are that, unlike Daisy and Waluigi, he's somehow amassed a dedicated fanbase and that he got a good number of votes in that character poll--but that's kept in check in my mind because (also unlike them) putting him in would mean that he'd have to be picked over a different Square-Enix character.
Edit: Actually, I'm not even sure Daisy is an apt comparison either. She was at least in one main series Mario platformer.