According to your logic, he cut Mewtwo and Roy, then only considered adding them again after Sonic was added, remade most of their data, then decided against it and scrapped them again. Also, if the roster was finished before Sonic was added, then why was Wolf added after Sonic?
I'm basing my thoughts on logic and reasoning, as I said, Mewtwo, Roy, and Doc were only cut due to Sonic's addition taking priority, this time there isn't anything that would do that. We don't have any character that would be so demanded that Sakurai would stop what he's doing just to add them, the most requested was Mega Man and he's already in the game. Characters will get cut due to time constraints, yes, but as there's basically no chance of another "Sonic situation" happening again, and he hasn't even set a clear release date, there shouldn't be any time constraints that would cause such. The game also seems fairly far in development, we know that it's been worked on for longer than Melee, and he has a team even larger than the one he had for Brawl, they're probably getting the work done quite fast.
Again, there's no solid proof until we actually get the whole roster, but seeing Toon Link (one of the lowest priority characters in Brawl) being finished already, I'm just really doubtful that we'll lose anyone this time.