Ubisoft says they delayed Rayman Legends because they want all 3 versions of the game to hit at the same time. Could this be a way of dealing with a regulation that Microsoft holds over third party games?

Microsoft reserves the right to demand publishers release multiplatform software simultaneously with Xbox 360 releases, even stipulating content parity. If that's the case, Ubisoft may have forced the Wii U version into September just by electing to port the game to 360. Still doesn't make the wait any better.