If the leak is correct, that puts us at 12 newcomers. I wouldn't bet on getting many, if any, more than that, since Sakurai's made multiple statements about fewer newcomers / less focus on character count / etc. In fact, ignoring the leak, I'd personally expect less than 12. Seeing another newcomer reveal that isn't one of Sal's characters would definitely be a strike against him.
I'm of the mindset that leaks are false until proven true, rather than the other way around, so I've been extremely sceptical about this one. On one hand, it's been sketchy in its delivery, and missed a pretty noteworthy character (Rosalina). On the other hand, though, it's nailed five out of six confirmed newcomers... granted several were obvious picks. And several of the characters in the second half of the leak are also obvious picks. There's room for a lot of uncertainty here, so hopefully upcoming reveals will start to clear things up.
Of course, there's always the possibility that only some of the information in the leak is true and legitimate. I'm pretty sure that happened with the Pokemon X and Y leaks - some very specific info turned out to be true, while other pieces of info (within the same leaks) were bogus. Could Sal have possibly tossed in some of his personal guesses along with WFT/Villager/Mega Man? It just seems feasible to me, is all.