Any character from Square is more likely than Geno as DLC. In general, Square has some of the most popular characters of the industry, all of them representing their own franchise, again, I have to point out, Geno in the end is still another Mario rep, and Mario doesn't need any help to sell it's games. Meanwhile, Square and Nintendo could be lazy, add Sephiroth and still, make a lot of people happy and sell the DLC plus FFVII on Switch. And that's just the easy route, any FF characters is worldwide more popular than Geno, all the Dragon Quest characters are more popular in Japan only, and both Nintendo and Square want to promote those games. Same with Bravely Default, Nier and even Kingdom Hearts. Even just as a retro SNES character, more people outside the smash fandom would prefer Chrono or a Secre of Mana rep.
All of Geno's recent popularity come from a vocal minority in the Smash fansom, that's why you can't search for the characters this days without coming across Smash on way or another, but for the general public, and a major part of the Smash Fandom, the are a lot of more popular Square characters to choice from, and a lot more valuable as DLC.
Again, Geno's best shot was in the Base roster, and just as Sakurai's request, as DLC, both Square and Nintendo have better characters to choice from, and just the more hardcore fans of Geno, the ones that have made their mission in life to promote the character, would complain for any pic nintendo could choice from Square. I mean, the worst they could pick is Noctis, and still, we all know he would sell better than Geno!