I haven't really been following Sora speculation due to a disinterest in Kingdom Hearts, so I'm unfamiliar with any points of evidence in his favor. What makes you so certain that Sora will be 5?
There's a few things but let me recount them:
-Firstly Sora is a Disney character, this means that Hero being a part of the pass wouldn't have much of an effect on if he were to be added or not
-Disney JP's vice president has already given approval on Sora and said there would be no issue with having him
-Sakurai is a fan of the Kingdom Hearts series and has talked positively about it in the past
-Nomura and Sakurai have worked together before so that issue is out of the bag as well
-Namco and Disney recently worked together on the Disney Tsum Tsum game for Switch and also added PAC-MAN to that game, Namco is also the developer for Smash
-Nomura wants Kingdom Hearts 3 on Switch at some point, the original games are also coming to XBOX at some point leaving the door wide open for ports for Switch
-Following Kingdom Hearts 3's strong sales from the earlier half of this year, Square Enix and Disney have stated that the game will continue to have an extended marketing push moving forward despite having already released, this is because of later DLC releases such as Re: Mind and a possible Final Mix version
-Kingdom Hearts 3 has a presence at the Game Awards, having been nominated for best soundtrack and best RPG, like with Persona 5 last year it's possible they could use this as a way to tie-in a reveal but this is subject to change
-Finally there's the missing Chocobo and Geno costumes, strangely they didn't come with Hero but it's possible the reason that they didn't come with him was so they could save them for a character that fit with them better thematically, in this instance being Sora since Kingdom Hearts is a crossover of different Square franchises they would be better suited for releasing with him instead of Hero who is Enix.
That's everything off of the top of my head and I know some of it may seem a bit out-there but tbh there's a lot of signs that just really add up and it's too much for me not to acknowledge.