I've seen on April 1st on deviantART a journal about a Kotaku entry of a Rayman Origins sequel earlier, but today, it can be pretty much confirmed.
And is it just me, or does Rayman look just a little 3D-ish?
UPDATE[]
Yesterday, Ubisoft has bought some domain names: www.raymanlegends.com and www.rayman-legends.com. so we now kinda know the name of the RO sequel
but that's not the only thing I wanna tell you guys:
The leaked trailer can now be seen.
Until it gets removed from YouTube, but you can always search for it.