I'm pretty sure that if the Wii U can run games at 720p/60fps with extensive GamePad support and still display superior PS3/360 graphics, we will see some 3rd parties making games without GamePad support to enhance the visuals.
Then we could have 1080p/60fps + amazing graphics. The controller really eats a lot of ressources. But I'm pretty sure we will see awesome graphics in 2-3 years from now...