No details were given during Viacom's announcement, but the company did state that Rock Band 3 will "innovate and revolutionize the music genre once again, just as Harmonix did with the original Rock Band, Rock Band 2 and The Beatles: Rock Band." Despite how it's unconfirmed, it does appear that Harmonix will be at the helm for the third title in the popular music franchise. The developer will have another title to deal with as well for the holidays (Green Day: Rock Band was announced back in December).
Also, there is a possibility that the game may feature songs from the late guitar legend/god Jimi Hendrix. The possible inclusion of Hendrix comes from an interview last month from his stepsister, Janie Hendrix. Hopefully, if we're good enough, Harmonix could include some way to re-create Hendrix's on-stage rituals. Then again, lighting our plastic guitars on fire wouldn't be environmentally friendly.
Stay tuned as more information surfaces.