Here are my predictions based on the number of potential characters left:
If box theory is correct and there are only two characters left in the base roster, then the two that are left are Ken and Incineroar. This isn't exactly a controversial opinion, obviously, but it's one I hold.
If there are 3 characters left, then the 3rd is Vergeben's Square Enix character, and that will be Geno. Not Sora, imo; Sora, if he got in, would probably be as DLC. He might not be impossible to obtain the rights for, but he would be hard enough that I couldn't conceivably see him being a character that Sakurai would put in the base roster. Geno could be DLC too, but only if there are only two characters left.
Finally, if there are 4 characters left, Shadow will be the fourth as an echo of Sonic. Box theory would suggest that only Ryu is getting an echo past this point, but if there are 4 characters left, box theory is completely wrong anyway, and Shadow has been a decently popular request since Brawl, believe it or not. I don't think Steve is in the game at all until we get more solid evidence. Minecraft being represented isn't hard to believe at all, but, while I wouldn't mind him, Steve doesn't seem to meet all of the "criteria" Sakurai usees when deciding characters. If he did get in, I think he would be called "Crafter" instead of Steve in the vein of Pokemon Trainer and Villlager, anyway. I may be wrong on this, but this is my gut feeling.
4 is the absolute maximum amount of characters we have left, and even then, that would only consist of 2 true newcomers and 2 echoes. I don't see a reality where we have any more than that left for the base roster at this point.