Or they could just download one of the PC games online that turn the keyboard into the guitar in Guitar Hero. These free games also regularly get new songs to play, where as Guitar Hero players will need DLC or the next edition of the game.
You push people away from piracy with gimmicky peripherals (not saying GH is) and they get even more reason to pirate (download the game and buy a cheap second hand guitar controller on ebay).
I'm sure if a new GH edition (or any game for that matter) is good and a much bigger step up from it's predecessor then it would encourage more people to buy, I mean, the Guitar Controller gets more of an update then the games themselves do between editions.
EDIT: I should say that I don't condone piracy, but forcing people to buy excessive amounts peripherals is ridiculous (i.e I'm not buying the wii balance board, the wii sports accessory pack, mario kart steering wheel and wii zapper just to play a few games).
