Sakurai has said that certain characters were chosen from the ballot such as Simon, King K. Rool, Ridley and Banjo & Kazooie. With that being said, plus the copyrighted songs, the lack of Mii costume, the starling, Megasmilax on Palutena, having a separated splash art even being just a costume on WiiU, Nintendo on Twitter about SMRPG, the 2 decades fan demand placing Geno in a solid hill, the recognition Geno has being a costume before and a spirit now, for me it’s almost 90% probably that he will be in. I think if Sakurai didn’t had Square permission or the will to put it in, he would already have deconfirmed him. And we are not talking about a dead character with no requests, we are talking of Geno, who has been in the Top-Polls since Melee, and I can say by now that he, after Ridley, Rool and Banjo was confirmed, is the highly requested character and number one character to fulfill the roster. Maybe Sakurai will place Geno in a better moment like in a Direct when they reveal Banjo’s moves; maybe as a Bonus DLC or maybe as character 4 or 5. His story is perfect, being partner with Mario, his moves and design, born in a Nintendo system, etc.
We already have many reasons to call Ultimate a dream come true with Mario, the rest of Nintendo cast and all the 3rd parties, but it’s unbeliavable all the noise that Geno has been doing EVEN coming from just one game. Maybe after the Pass, they will close the DLC with another Mario rep and that would be him. Sakurai is smart and he can’t reveal all at once, he has to keep us hyped somehow and at this point, I doubt that he will release Chocobo hat and Geno costume later. Chocobo will return probably with Geno being playable; and maybe Mallow as a spirit, trophy, part of the final smash or who knows, maybe as a tag team. I would prefer Geno alone if I have to choose but maybe they put Geno & Mallow as a special couple that you can switch in gameplay (like Pokémon trainer, not like Ice Climbers). That would make him even a more unique fighter for the DLC, like Joker has Arsene; Hero has RPG moves, Banjo has Kazzoie and the feathers; Geno could have Mallow and a special system also. I doubt that G&M both will be fighters separated, the options more likely are Geno alone; or both as a tag team in the same slot. But in the end, I just see Mallow just being an extra (spirit, part of the FS or Assist trophy).
There are plenty of ideas to make his trailer also. Think of the chances including dolls of Mario, Bowser, Peach as the Smash 64 intro video. Or starring Rosalina, Luma or Kirby.
Im pretty sure Geno will be fighter #74, #75 or #76.