When Ubisoft decided to push back the release of Rayman Legends early this year there was quite a bit of outrage from the Wii U community. At the time (February) it was one of very few exclusive releases due out, and to add insult to injury the reason for the delay was to allow for the development of PS3 and Xbox 360 versions to catch and release simultaneously.
Fast forward until now, with three weeks remaining til the release, Ubisoft have announced that you will be able to play as Mario and Luigi in the Wii U version:
"Exclusively available in the version for Nintendo's Wii U system, players will be able to unlock skins for Rayman as Mario and Globox as Luigi after 20 minutes of gameplay."