The one thing that is of some credit to Geno's chances is the fact that Sakurai has gone on record stating that he very much so wanted to add Geno to Brawl but it didn't work out. Fast forward to SM4SH, and Geno is understandably missing while Square's biggest character in Cloud gets in. But Geno makes the unprecendented jump to a Mii Costume, and is the only Mii Costume in both SM4SH and Ultimate to get it's own splash screen. Geno then makes the jump into Ultimate with a spirit, and despite all the returning costumes slowly making reappearances with the DLC and being in a perfect position to come with Hero but so far being nowhere to be found for 6 DLC costume waves now.
Whether you like Geno or think he's likely, Sakurai has shown himself to be a big fan of the character and, again, has tried to add him to Smash in the past, which sets him apart from characters like Ridley, Villager and Chrom, all of whom he had negative things to say about in the past regarding their chances. There is none of that for Geno, so even if the coincidences surrounding the notable absence of his mii costume aren't indicative enough that something is up, I at least hope people understand why the people that support Geno in Smash have hope for his chances in FP2.
And I say all this as someone who has never played SMRPG and doesn't have the same emotional connection to the character as others do. I just like Geno's design and the possibilities for his moveset and can see the potential for what he could be.
But the irrelevancy argument for Geno means little when fan demand for Ridley, K. Tool and Banjo got all of them into Ultimate. If Geno gets into Smash, it’ll be because of the Sakurai’s desire for him, boosted by the same long-standing fan demand Geno has had in the Smash community. If he wants it to happen, he’ll make it happen, and if it doesn’t, then that’s that.