In a press release issued today, the company boasted that World Tour, commonly referred to as Guitar Hero 4, will be the "first game ever in the Guitar Hero franchise to allow in-game downloadable content on Wii."
It is not yet known if the content refers to new songs or just the sharing of user-created tracks, the latter being a functionality all editions of World Tour are known to include. PlayStation 3 and Xbox 360 Guitar Hero entries have used downloadable content to add new songs to the game, some of which are sold and some of which are given away.
Few Wii titles have supported downloadable content due to the system's paltry 512MB of internal storage. While that storage can be expanded with an SD Card, at present, the Wii will only execute downloaded content if it is located within that 512MB internal block.
Activision subsidiary RedOctane had previously stated it was looking into DLC support for the Wii edition of Guitar Hero 3.
Harmonix, which created the Guitar Hero franchise before it was acquired by MTV Games, stated that the upcoming Wii version of its multi-instrument music title Rock Band does not support downloadable content due to storage concerns.
Instead, the company is providing additional Rock Band tracks to the Wii and PS2, which also lacks DLC support due to storage issues, in the form of an expansion disc.
I know people are down on the Wii's general lack of DLC support, but I applaud Activision's attempt to make it work for the Wii with GHWT. I don't mind buying expansion discs for new tracks as a replacement for DLC as long at the majority of songs are interesting, but I will miss not being able to play full albums like the Pixie's Doolittle that will never make it via expansion.
Sounds like you're talking about Rockband with it's expansion discs - that might not have been such a bad way to go about it if the game itself wasn't gimped. The PS3/360 versions are much better games, regardless of DLC.