Harmonix seems to have unintentionally confirmed that Lego Rock Band is in development.
This was revealed via a leaked PDF showing an early version of Harmonix senior designer Dan Teasdale’s GDC discussion called “Dirty Deeds Done Dirt Cheap: Design Lessons Learned From Rock Band.”
Apparently Lego Rock Band was supposed to be officially announced prior to GDC 09. The game is scheduled for release this year. One of the slides seems to indicate that the game is scheduled for release between Rock Band: Unplugged for PSP and The Beatles: Rock Band.
Via Kotaku