Guitar Hero franchise - it was just a hiatus to keep the game out of sight while a reboot is being planned to reinvent the series.
Kotick stated in an interview with Forbes Magazine, "We said, you know what... we’re going to take the products out of the market, and we’re not going to tell anybody what we’re doing for awhile, but we’re going to stop selling Guitar Hero altogether. And then we’re going to use new studios and reinvent Guitar Hero. And so that’s what we’re doing with it now."
Activision deserves most of the blame for not only running Guitar Hero into the ground with oversaturation of the market, but the entire music game genre itself. In 2009 alone, the company released five different Guitar Hero titles, including Guitar Hero 5 and Band Hero within two months of each other!
At the moment, the only new entries into the music genre coming later this year are Dance Central 2 and Rocksmith, while Rock Band 3 still enjoys healthy DLC sales.