Rock Band hasn't exactly been doing nearly as well as it used to either. Did you miss that Harmonix was unloaded by Viacom for practically nothing a month ago due to poor revenue? The music genre is all but dead, and while RB was the white hat of the battle, the sheer amount of glut of music games from all parties is what turned everyone off. The biggest problem was that after six years of music games, the gameplay was still the same, even with the additions and improvements you were still watching a rainbow highway and matching colors.
"Maybe their music genre. "
" we have seen rapid declines in the music genre "
I think everyone suddenly realized it was cheaper to play air instruments and listen to an MP3 of their favorite songs instead of spending hundreds of dollars on the game and only liking 1/4 of the songs.