Honestly the only 3 characters that I have any reason to believe are in the game are: Ken, Shadow, and Isaac.
Ken simply because if any echo fighter is going to make it into Smash, it's the OG echo.
Shadow because his AT is still missing + he's the only 3rd party character to be an assist in multiple games. If he's not an assist, I see no reason why to cut him (unless he's DLC).
Isaac mainly because of the Ratholos pic and (possibly) the new Golden Sun item shown recently. In my opinion, he's the only newcomer from the banner "leak" that actually has anything pointing to his inclusion through OFFICIAL released content.
I'd agree with the first two, but for very different reasons. I think Verge's track record is good enough to take what he says seriously, so in addition to the "leaked" image of Ken, and he has no other rumors contradicting his inclusion. I couldn't make the AT argument for Shadow, as that can be said for many ATs, including but not limited to Skull Kid and Tingle. I would say, however, Shadow benefits from being a missing AT, in combination of being an easy echo.
Isaac's a bit more tricky because it's solely dependent on interpreting that "official" post. I feel like Banjo & Kazooie reverting to their N64 designs, rather than their Microsoft designs, is a sign from an official source, added to Verge's rumors that Minecraft (Microsoft) content could be in the game. It's equally plausible, when combined with rumors/official statements. Similarly, we have multiple rumors surrounding an SE character, when combined with fan demand, lines up with Geno (with Sora, purportedly, being hinted at for DLC). The only characters with nothing hinted at would be Mach Rider and Chorus Kids. But even then, Sakurai's image of the toy gun (so, an official source much like Isaac's) lines up with Mach Rider, if interpretation is allowed. But many interpreted that as being a sign for Elma, so it's an interpretative conclusion.
And also, while we only have rumors concerning Incineroar's inclusion, which is seemingly contradicted by this questionable banner, the fact many insiders seem to suggest Incineroar's inclusion is grounds for dismissing the leak (depending on assumptions), means Incineroar's possible inclusion carries some weight.
Of course, these are all my opinions, as I prefer rumors over interpretations, in how I consider something to likely be, but this is where I see the various likelihoods of the banner characters to be.
EDIT: Whoops, somehow combined Ken and Shadow in the Verge stuff.