Finally, Activision has a good idea for the Guitar Hero series. *awaits "Knights of Cydonia" drums and vocals*
There are no dildos in Guitar Hero DLC. But seriously, 3 releases in one year? Just, no. I'd rather have it as DLC as well since I could buy some of my favourite songs instead of the whole package.
With DLC there should be no need for 3 in one year. 2 is just able passable. The idea of having the DLC is so it's constantly updated without having to release another sequel with more songs.