If it is possible to easily make a game multiplatform (as Guitar Hero undoubtedly is), why wouldn't you put it on as many systems as you can? The Jackal is right; the producers would have to be stupid not to put it on the Wii. From a business standpoint, it's a no-brainer. The Wii has a large market. Specific controllers are already needed to play the game, so trying to adapt the game play is a moot point. They have nothing to lose and everything to gain.
Generally speaking the disc size wouldn't affect how many songs you could have since your average Guitar Hero "Fret file" wouldn't be beyond a few megabytes. Most of the information will be graphical stuff. But yes, I will most likely get GH3 for the Wii rather than my aging PS2. Those who lack the foresight to understand how awesome the concept of a wireless Guitar Hero controller is should seek help...but that's just my opinion.
There is no signature here. Move along.
Customer basis is a good reason. However I except the whole damn blue ray to be filled with music.
However they will probably never give you that much music to play, the cheap bastards.
It's still Fisher Price.