They revealed a crapload of 3DS stuff at last year's GDC, and they said that we would get Wii U news before E3, so GDC absolutely HAS to be a place they tell us something.
Yeah, i think so too. Between GDC and a Nintendo Direct, i think GDC is the best way to show or talk about Wii U, because the media will be there as the rest of the industry and would be really good for Nintendo to have people see for themselves what a video can`t show.
On topic: according to GAF, there´s a rumor that Crytek might show something. Most likely an engine demo.