Fake or not, I'd say him not being included in the Mii outfits released alongside Hero is a good indication that he may be coming. Granted all the Mii costumes that came with Hero were only Dragon Quest related, but all the same it would make sense for the Smash 4 Square Mii costumes to release alongside the Hero, much like the Sonic costumes released with the Atlus rep (Atlus being a subsidiary of Sega) of Joker.
Not only didn't the Geno costume get released with the Square fighter, but so too didn't the Chocobo hat. Seems to me that if Geno does get in as a fighter, then the likes of the Chocobo Hat Mii costume would instead come alongside that. (would love to see some Chrono Trigger and Mallow Mii content to release at that point too).
Still 2 of the 5 fighters coming from the same third party rep does seem unlikely which is what is holding me back from thinking it's a near certainty at this point.