The Omega DLC for Mass Effect 3 will not be available for Wii U when it launches November 27, according to BioWare's official Mass Effect Twitteraccount. The DLC will release on PS3 and Xbox 360 for $15.
When asked about future DLC offerings for Wii U, BioWare's reply was "never say never," which either hints at the possibility of DLC such as Omega launching on Wii U in the future, or the Mass Effect team was listening to at the time.