I would love Vergeben having incorrect info at this point. Not cuz I don't like Incineroar or Minecraft, but just to make the speculation a little more interesting til that last character reveal
I would love that, because it's mainly been Verge, in combination with these theories, that has made speculation so dull. However, I have to admit that he's gotten a lot right, and have considered him trustworthy since Simon's reveal--I want to avoid being in denial.
That being said, I can't see Nintendo going to Microsoft for just a stage/assist. Only if the talks began after the roster was decided. I feel like something must have been the impetus to begin those talks, and 2015 with Banjo's popularity seems like the most appropriate time. Add to that Microsoft going back to Banjo's N64 design--that doesn't sound like a Microsoft/Rare decision, but it does seem like a Sakurai decision.
But all of that is meaningless if all that is left is what's rumored (still don't believe box theory, as I believe SE rep is in the base). But these all do align with copyright theory.
Was the Smash 4 E3 demo available or streamed before Pac-Man was announced? Can't really remember when Pac-Man was revealed in relation to the rest of the event as I was asleep at the time, I just remember it didn't happen during the main presentation, so maybe there's something to be found there.
I believe the first demo was after Pac-Man's reveal (though it's difficult with Pac-Man, since it's copyright owners are also helping to develop the game)--that being said, Pac-Man wasn't in the Treehouse demo. I could be wrong, though I've searched for an early demo build and found nothing.