Found this online
"While owners of Guitar Hero III on other formats are blissfully enjoying their new downloadable content, Wii owners have not. They've been left out! Hopefully not for much longer, though, as Red Octane have told Nintencast that they're hoping to have some DLC ready to go sometime early next year. No idea how they'd deliver it, where you'd have to store it or how you' pay for it, but then I guess that's the cause of the delay in the first place. On the off chance you're reading this, Nintendo, Wii Shop Channel purchases to an SD card would be brilliant, thanks. "