It's no rumour, this game will definitely be released. In Australia it will be released in Summer, in America it will be released on the 22nd of June. Personally, I'm going to pre-order mine either now or within the next few weeks. This is too good of a game to miss.
Most people know Guitar Hero, normally you'd buy the Playstation version then plug specially made guitars into the playstation or computer then choose from different songs and play in an easy way. This game has already been tested on all types of different game testers, newbies who've never played Guitar hero before until now, Experts who can play Dragonforce on expert super speed and real guitarists.
Game play is easy, they've come up with a thing they call the Guitar grip which you plug into the GBA game slot in your DS. Although the Guitar grip is fitted for the DS Lite, only just smaller than the size of the DS lite, but has an adapter for the old version of the DS so they can still use the Guitar grip.
Due to comments by the game testers, they also designed a pick shaped stylus especially for the game, along with a wrist strap for support since the DS was held book style when playing. Due to all these game play features, it makes game play really comfortable and easy to use on the road or whilst in the car.
I'm assuming that there will be no DS download play because obviously people playing through download would not have a pick shaped stylus of a Guitar grip anyway, they'd only have that if they had the game in which case they wouldn't need download play.
I'm sure that the multi-card multiplayer will be more fun than money raining from the sky. Stores in America such as Toys R Us are already hosting game testing days and giving out official guitar hero promotional items such as stickers with their logo, wash off tatoos with the logo and dog tags with their logo.
Stores in Australia are also doing promotional things such as giving out free video demo dvds and an official Guitar hero stylus with their logo on it, or an official guitar hero pair of head phones also with their logo, to anyone who pre-orders the game.
Although this would have costed them thousands or maybe even millions, once this is released the stores will be packed with people wanting to buy this game. Anywho, I'll try to get in a new review on the released version next month but I live in Australia so I won't have access to the game unless I order it online. Personally, I think it's worth the wait, sure if I got it soon I could be the best player in Australia, but I couldn't be bothered waiting months to do multi-player! :P