My problem with the leak so far is thus:
While there is some evidence for it, there are some very glaring points against it that seem to be overlooked or shooed away.
So far, these are the points that I believe have not been discussed successfully enough to give it a "true" verdict for myself personally.
1. Ambiguity of terms.
Oh look, I'm bringing Villager and Greninja up again.
"Animal Crossing Guy"
Mentioning a series name like this is where I feel the key difference lies. My point is thus:
There are no real "recurring" characters in Animal Crossing that can be construed as a main character.
So, we have to look at a character that's the face of the series, that everyone knows. In my eyes, (as well as a fair few other people) this is Tom Nook. I would argue that, if you're saying "Animal Crossing Guy", my initial reaction would be to think of Tom Nook.
The main attraction and features of Animal Crossing are the animals that you share a town with, lending further credibility to this. Everyone remembers that annoying racoon that makes you pay an assload of bells just to get your house. In this way, the most memorable characters are the main focus of the Animal Crossing franchise. This time around, it would be Isabelle and Tom Nook.
"Pokemon from X/Y"
I find it an absurd notion that he would not mention Greninja by name. If he had access to this information, he would have known it was Greninja and in that case, why not say Greninja?
The evidence being given for this is that Sakurai said that they had an open slot for a Pokemon from X and Y, yes.
However, if you listen on a little further? They chose Greninja very early and Sakurai worked on him in the same night. So, Greninja was basically decided on overnight.
If he knows the other characters, why not Greninja? At this point, the roster is very likely not to be finalised and the "fringe" picks such as "Chorus Men" would be done near to the end. Seeing as Pokemon is such more of a prevalent franchise than Rhythm Heaven, I am 100% certain that he would be decided on before them.
TL;DR: If he has access to more of the "strange" pick information (WFT, Villager), why did he not know about Greninja, when by then, he was most likely finalised?
2. Too little information and looking beyond the face value.
This is a short and brief point, nowhere near as much as the previous point, but if you listen to a lot of people here, you would believe that the Chorus Men are confirmed, just because there's a Rhythm Heaven enemy in Smash Run.
Could it be possible that that enemy was chosen because it's an iconic enemy? There is zero correlation between an enemy being available in Smash Run and a character being playable. A Poppant is an enemy in Smash Run, does that mean for example a Primid is playable in Smash? Of course not, but that's the logic that is being followed.
3. Timeframes.
While it may not have been explicitly stated, it was very heavily implied that Shulk, Chrom and Chorus Men would be shown at e3. They were not.
For me, these points are enough to discredit the leak as a whole, along with the fact that Rosalina was not predicted. If Rosalina had been predicted, along with the others in this leak, I would be more inclined to believe it, but with the information and disrepancies withstanding, I just can't, there's too much evidence against it for me and while it cannot be proved either way, I feel the evidence comes down on the side of false. However, if it is proved to be true, I will state that I was wrong in this thread for everyone to see.