Harmonix recently announced the next edition of Rock Band. It looks awesome. You can either get the whole new set of upgraded and improved instruments, or you can use your Rock Band 1 instruments. Also, they will be allowing third-party accessories and instruments to be made and sold. They want Rock Band's instruments to be like a real instruments: everyone likes different feels and styles of instrument.
Another great thing about Rock Band 2, is that you will be able to use all of your Rock Band 1 songs with the Rock Band 2 game, and vice versa. Oh, yeah, and Xbox 360 owners get to enjoy it as early as September of this year. Where Wii, PS2 and PS3 owners need to wait until "later in the year". There will be tons of more details and goodies to pour over after E3, where more will be announced. For now, here's a really good interview via IGN. You can also see the sweet new guitar pictured below. It will hopefully be wireless, and is said to be quieter and it feels like a real guitar.