There won't be another Rock Band released in 2009 as Harmonix are focusing their full effort on the upcoming Beatles game they are working on. There will however be a Rock Band 3 further down the line. Considering Harmonix recently reached a milestone with 500 downloadable songs for Rock Band 2 it's safe to say that we won't grow bored of their game anytime soon - and more music is coming.
Even though I'm personally not that excited about a Beatles game (singing Yesterday one hundred times in school does that to you), it is nice to see that Harmonix dare avoid the trap of annual sequels. Rather than milking Rock Band dry, they can make sure they have something special for us next time around.