Though not through the usual means, EA and Harmonix have that Rock Band 3 will hit stores in its usual release window, the fall. The announcement came way of the official Rock Band Facebook fan page, teasing that this iteration of the franchise will revolutionize the genre, again.
"Harmonix is developing Rock Band 3 for worldwide release this holiday season! The game, which will be published by MTV Games and distributed by Electronic Arts, 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. Stay tuned for more details!"
That's all the word there was, and nothing about when details will come. As Rock Band has been a pretty solid franchise, it wouldn't be a stretch to believe they have something up there sleeves for Rock Band 3.
Source: Rock Band Facebook Fan Page