I just read the interview posted on IGN.com with the developers of Guitar Hero World Tour for Wii. Sounds like it is going to be one sweet game. Here are some of the highlights from the interview.

"Wii owners lapped up Guitar Hero III. It's quickly becoming the best-selling version of the game."

IGN: You've announced in-game downloadable content for the Wii. Not even Nintendo has done in-game downloadable content yet, so how did you end up being the first disc-based game to feature it? How will it work with the Wii's limited internal memory? Will you be able to use SD cards?
"...I know there has been detractors who say the Wii can't do DLC for various technical reasons – and they are dead wrong. The system is quite capable..." <-- Huge snipe at Rock Band and their lame excuses
"...GHWT Wii has an in-game Music Store, which allows players to preview, purchase and download new songs as we release them online. Players can purchase songs using their Wii Points. It's really easy. You can download to the Wii System Memory or store songs on an SD Card, called the "Rock Archive. We have a new feature called "create-a-set list". So when you want to play songs you have purchased, you just make a custom set list of songs you wish to play from the Rock Archive, pick a venue and play!"
"If you accidentally delete a song, or don't have an SD Card and have run out of room in the Wii system memory, you can always re-download the song for free. "

IGN: Outside of the downloadable content, will there be any online multiplayer like in Guitar Hero 3?
"Heck yeah!"
"Believe it or not, the number of active online GHIII Wii players is almost equal to Xbox 360."
"With the introduction of the new instruments, we can do eight players online – and still maintain a high quality experience. Players can go head-to-head (such as two vs two, three vs three or Band vs Band), play cooperatively or play the career mode online."

DLC is done in game with Wii Points. The Wii Shop Channel is not involved. If you delete songs, you can redownload them at any time for free.

The Wiki page says that previous GH guitars will be compatible with World Tour.

To me, it looks like Neversoft's version of Rock Band gone absolutely right. I mistakedly bought Rock Band for the Wii and after taking a glimpse at World Tour, I can easily say that Harmonix definitely hates Nintendo. Neversoft must have some respect for the Wii however, since they're putting much more effort into World Tour than Harmonix did with Rock Band. Hopefully, I'll be able to sell it online for a good price and have enough money for this incredible-looking game.

Yeah, Guitar Hero World Tour sounds very promising. When RockBand for Wii was released, I did some research. I love RockBand, as I've played it a lot with friends on the XBox 360, but I was unsure about the Wii version. Lots of things, mainly related to online play, was stripped out of the Wii version and that didn't make me happy. I read this same interview on Guitar Hero World Tour and it made me realize that it's worth waiting for instead of just buying RockBand now. I think RockBand was released for Wii half-assedly (is that a word? ) just to make sure it was available way ahead of time before Guitar Hero World Tour and before RockBand 2 comes out for 360. I'm really looking forward to GHWT ... I believe I read somewhere that the guitars from GH3 are compatible ... but if not, at least this game has got a lot more meat to it and I won't feel completely ripped off from the game if I do have to buy a new guitar.

I'm looking forward to it.

Oh, and as for the comment about the Wii making online play more difficult ... I wouldn't be surprised if Nintendo's online approach made certain things to implement a whole lot more difficult, but as the interview pointed out, it CAN be done. It probably just requires a different approach, an approach that RockBand didn't feel like taking.