Honestly? There's a lot of evidence pinpointing one or none of them will be Nintendo characters.
The majority of companies that are represented have strong relationships with Nintendo (like Atlus, Rare, some more leeway with Square-Enix). Not out of the ordinary to suggest other companies are going to get the same treatment.
But Nintendo have more fruitful relationships with other companies. Ubisoft, for example. Koei Tecmo, Level-5, Capcom. If I were to be as realistic as I can, I think Koei Tecmo will pick a character. I know a lot of people are rooting for Ryu Hayabusa, but I wouldn't rule out Kasumi from Dead or Alive. I believe the franchise director said if he could choose any of his characters, he'd select Kasumi. Without hesitating.
The next character will almost certainly be announced quietly. You can't exactly top Sephiroth, so Fighter #9 will probably be revealed the day after they announce their reveal and won't be tied to an event. Fighter #10 might be a similar story.
The final character would be huge. Someone completely surpassing expectations, a full on break-Twitter character that makes Ridley's, Steve's and Sephiroth's reveal look tame. Nintendo doesn't want another Corrin/Byleth situation again. I was guessing Master Chief from Halo, but I'm second-guessing that now he's in Fortnite. For all we know, it could be a Fortnite character or maybe Waluigi. Something shocking.
If the character's company is getting on well with Nintendo they've got a shot. I'd be chuffed to see Rayman, Crash, Professor Layton (obviously), maybe an indie rep like Hollow Knight. Or maybe someone completely out of left-field like Gordon Freeman. But that's just my fanboy side talking.
