Considering Nintendo is choosing, not Sakurai, them picking Geno would mean it would be from pure fan demand, and basically nothing else. This is from Square Enix, a company with a vast selection of many famous characters, or at the very least from big titles throughout the industry. Not to say any of these particular characters are likely, but you’ve got names like Tifa, 2B, Neku Sakaraba, etc...
I don’t think it’s impossible for Geno to get in. He’s a character kept alive by key fan support over the course of many years. However, I’ve never been convinced that “popularity” is a strong enough argument to overlook other obstacles in the way of a character being added.
Essentially, I don’t see the appeal to non-hardcore Smash fans to pick up Geno, I don’t see the appeal for Nintendo to go for him aside from the appeal to hardcore Smash speculators...Square Enix, if they wanted to make money off of a “dead” character, has that financial gain, but...
Like, personally, I always envisioned Geno as a “hype” pick. But I’m not personally convinced that he will be added.