Guys, we SERIOULSY need to make clear that the Ninka leak did NOT have Mewtwo and Ridley in it. Idk, just make an annotation in the OP or something.
Besides, everything the gematsu leak stated bar Chrom and CM has been confirmed so far. And it has been widely speculated that the info he got was outdated so it makes sense he knew about Chrom and a "Pokemon from XY"
EDIT: Can someone actually confirm if this leaker is indeed the actual Sal Romano? Although I guess it doesn't matter in the end since he does not reveal anything new, I guess
Sal Romano isn't the leaker, it was the guy emailing him that was the leaker.
That reminds me, I'll speak of my full theory on the leaker and why it turned out the way it did. I feel that that the leaker only got the information by seeing the planning documents of the roster (that was written before the game got far into development). It is unlikely he learned of the characters from the footages themselves.
He got Villager, Mega Man, Wii Fit Trainer, Little Mac, Greninja (listed as Pokemon from X/Y in his leak), Palutena, Mii Fighters, Pac-Man and now Shulk correct. Wii Fit Trainer isn't exactly the character you can come up with easily, so it was extremely unlikely he was guessing that. And the fact he got a goood chunk of the newcomers correct kind of says he really saw what was planned for the game.
Only character he got outright wrong so far is Chrom, but Chrom
was actually planned for the roster as Sakurai has stated in an interview on why he didn't make the cut. They decided later that he would be just another blue-haired sword fighter just like Marth and Ike, and went with Robin instead as he is not only the other main character, but also very unique. (While the same argument could apply to Lucina, she only got in because she was originally planned as an Alt for Marth but ended up having different properties that wouldn't work as an Alt)
As for Greninja and how he listed him as "Pokemon X/Y", it is very likely because the planned roster had that name (or something similiar). In the E3 roundtable (I think the same roundtable that revealed Pac-Man), Sakurai was asked how Greninja's inclusion came about. He answered that he had Pokemon X/Y as the slot name for planning the roster as Pokemon X/Y was still in development at the time. He and the team were given finalized Pokemon designs from X/Y and they chose which one they felt would be best for the roster, which turned out to be Greninja.
So yeah, I feel the leaker was relying on information he saw from the planning document and has stuck with that until it became apparently outdated (when Chrom was deconfirmed).
Feel free to add on to this or correct me, I kind of went off by memory.
EDIT: Whoops, didn't know we were on the next page. Some probably has beaten me to the punch, so I apologize in advance.