Rock Band isn't much better.
Rock Band came up with something new, something innovative - the Keys are the most awesome things I have ever played (until my keyboard broke that is ). Harmony vocals are also killer fun. People just quickly judge them to be "just another pile of plastic instruments" when they are NOT. They're actually real instruments, the real deal (at least the Squier and the Keyboard).
Latest GH games have simply been new song packages. Their game engine was horrifying (vocals, anyone?) and GH games' music libraries mostly covered metal and rock only. They added nothing new to the genre. RB, on the other hand, has new songs flowing into the game every few days with official releases every week with loads of different genres included.
I do not think Rock Band will die. The Guitar Hero genre dying, though.. no surprises there. Glad it's gone.
Also, thread on this matter posted on RB Forums by Harmonix employees.