There've been rumors recently that Microsoft might be shutting down Xbox Live Indies (fueled by their confirmed discontinuation of the XNA Framework, which powers all XBLIG titles). If the Indies store (and Creators Club) go away, it seems like RBN would have to die as well -- unless Microsoft were to create some kind of new platform for it, or bend their own publishing rules.
Meanwhile, Valve's announced their intentions to create a Linux-backed Steam "console" for TVs. They have a reputation for being very easy to work with, and for being supportive of user-created content. The Steam platform is also friendly to free-to-play games -- and since so many people already own instruments (which are either USB, or PC-compatible through a standard Xbox wireless controller dongle), a free-to-play Rock Band where you buy songs a la carte might bring in customers.
I know we've all got lots of DLC we don't want to lose, but this seems like it might be a great way to give Rock Band a shot in the arm: having RB3/Blitz be launch titles for a "new console" (so to speak) would probably be good exposure for the brand, and it'd certainly help solidify the Steam/Linux platform as a good way to play serious games in your living room. Really, what's more of a TV game than Rock Band?