The fact that Sakurai has, two days in a row, shown images almost directly from the leak, shows me that he is not only aware of the leak, but playing into it.
This bodes well for my theory that he expected (or assumed) the roster would either be leaked, or that it easily could be leaked, (as Brawl's was) or... at least that the games roster would be leaked moments after the game cartridge was received (or sold early) at a location in Japan. In short- the likelihood of the roster getting out early, to the masses, was almost inevitable. The community for this game is huge- just look at E3 being won by smash single-handedly; or the regularly updated website with info on the game (over a year old); or this forum (and all the others) with thousands of regular posters.
Sakurai would have known of this being likely
And given Sakurai's love for surprise, and the fact that the roster was not told to us before the leak, and in fact, this month of updates before the release has been not only nonchalant but pretty abdicative of responsibility...this just... really screams that he has more characters than what COULD have possibly been leaked, or at least, it screams this to me. Or, in other words, that the cartridge never had the full roster in the first place.