Rock Band VR was announced at the Game Awards tonight, slated for release sometime in 2016.
Harmonix has spoken about the "incredibly exciting" opportunities afforded by virtual reality before. Back during E3 this year, Oculus also announced Harmonix as one of their partners, which also included Square Enix and Insomniac Games. It wasn't until tonight's Game Awards that anything was actually announced.
The upcoming Rock Band VR is a separate project from this year's Rock Band 4, made specifically for VR and the Oculus Rift exclusively.