Sources: 1 2
Okay, this guy says he has an "industry source", so it can be true.
Rayman is a trophy, Nintendo of Canada tweeted he was playable (before "clarifying" they meant Pac-Man was playable and Rayman was a trophy).
The Mewtwo in that image, looks a bit off though.
I really hope it's true though.
I loved Rayman Legends, and he'd be an interesting character (I'd love to see how they'd make an amiibo for him).
They also showed an image with a "Shop" icon for the Wii U version.
If you're interested this guy analyzed these images really carefully, and noticed some in-depth features of the Wii U Roster most people haven't noticed, and the fact they show up in the Rayman images as well: Here is the link
I found this image not listed on the news sites of the 3DS menu with Rayman: