Guitar Hero: Van Halen is confirmed, out around Christmas. As for Rock Band, Green Day and Pearl Jam are strongly rumoured but nothing's actually confirmed yet.
As for what I'd like them to do... well, I'd like them to stop with the band-specific. I see why they do it, but they just don't have the mass appeal of the main series games. I haven't got Metallica and I won't get Van Halen, mostly because my days of serious plastic guitar playing are over so I don't want to spend hours grinding away to get better at difficult songs. I did, however, get the Aerosmith one and I'm getting the Beatles Rock Band because I just love those bands.
But, disregarding my opinions on the above: I'd be here all day if I listed all the bands I'd like to see a full game of, so I'll spare you that. I'll just say Radiohead for now.