With Gameloft's Guitar Rock Tour 2 heading to iPhone it was most likely to think that they are planing a future DSiWare release. On the official Guitar Rock Tour Twitter account from Gameloft this statement was made:
"It's not scheduled yet. Guitar Rock Tour 1 has just been released on DSiWare :) But it may come one day... Stay tuned!"
Gameloft also release a teaser video of the iPhone version, which can be found here.