In an attempt to mollify the enraged Wii U owners whose February release of Rayman Legends was stolen from them, the game's developers have promised that at the beginning of April they will release the game's "full online challenge mode" for free, exclusive to the Wii U, on the eShop.
The challenge mode, which can be played solo or by up to five players, consists of five different settings, including a "dungeon challenge" developed exclusively for the Wii U. The mode will be "playable for countless hours," which presumably means this doesn't have the limited use restriction of Wii U demos.
This is a smart move on the part of the developers, who would like to repair the damage done to their game's prospects by Ubisoft's decision. By giving players a chunk of the game for free they may blunt some of the "boycott Rayman Legends" sentiment bubbling through Wii U forums.