You do realize that there's already an Ubisoft/Nintendo collaboration in the game, right? Rayman characters are already in the game.
Well, okay. But that was at least before they started dumping on Nintendo further. After all, Kerfluffle was in development for fucking ever. Even if there was going to be a Rayman DLC after the fact, I think the whole Legends thing and ransoming would have burnt that bridge completely.