Nintendo has announced via press release that the only playable demo in their booth at E3 this year will be The Legend of Zelda for Wii U.
Demos are going to be extended, which makes a lot of sense since it’s a game type that would benefit from 20-30+ minute type demos instead of the usual 5-15. Nintendo using all of their demo units also allows as many people as possible to check out the game.
I don’t think this is the only game they plan on showing during the event. My E3 prediction is that this is what you can play at the show, and they will also announce a few surprises, plus showcase a few new trailers.
If you’re not attending the show but want to see the upcoming Zelda game, Nintendo will also be live streaming gameplay.