Looks like there's going to be more controllers available than just the screen-based main controller for the Wii U.
Tonight, at Nintendo's pre-E3 video presentation, they released a photo of the new Pro controller which looks pretty much like an Xbox 360 controller with a Wii U logo on it, and hopefully with a better d-pad.
This may also be Nintendo's solution to only having one screen-based controller available for a console in a era when 2-4 player availability is the standard. You can also notice the recharge port at the top. In any case...can Microsoft sue for this design?