When will a game use two Wii U Gamepads?

[Lonely_Dolphin]

I remember hearing somewhere that the only way two gamepads could be used at once is if they're only showing 2D images. If that's true then Smash Bros. and 6 player Mario Kart are no goes. Should still work well for stuff like Pikmin, where the second screen is used as a map in stuff.