Alex Navarro (former Harmonix employee, now a writer over at Giant Bomb) has a fantastic, with several key Harmonix staffers, which you should read when you get the chance. But here are a few highlights:

On a possible Rock Band/Guitar Hero collaboration:

Alex Rigopulos: "I don't consider the fact that we were intense competitors in the past to necessarily preclude the idea that we could work together on the right thing in the future."

On Rock Band's future:

Greg LoPiccolo: "I'm confident in saying on the record that we have not abandoned the Rock Band franchise. We think there's a lot of creative life left in it, and we're extremely excited in the creative opportunities we think are there."