In response to a fan’s questions about DLC and the previous games, the Mass Effect twitter seemed to skirt around answering. The below exchange occurred.
It sounds like the DLC won’t be available for Wii U. Period. This may be because there had to be an all new team just to port the game for use with the Wii U’s unique gamepad. Any future DLC would likely have to be first ported by an outside team in order to work with the Wii U’s gamepad. This is a fact that BioWare and EA seemed to leave out when hyping the game.
One has to wonder why it was even ported with more DLC in the works, or why you’d even want to buy it for the Wii U. BioWare has already confirmed more DLC after Omega but won’t Wii U players feel left out if they are unable to obtain the full Mass Effect experience? It may be likely that somewhere down the line, after all DLC has been released, a team will port the DLC for the Wii U, but it seems as if Wii U players are getting a second rate experience compared to other players.
Source: Wii U Blog