Platforms haven't been confirmed, but we assume that'll be coming to both the Xbox 360 and PlayStation 3.
"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!" said the firm on its .
That's all we know right now, but expect more details from GDC soon.