Från 1Up.com:
Gitaroo-Man Live will appear on the PSP, a suitable place for the quirky sequel, as the console market is overcrowded as is. The game will reportedly be released on May 25th and feature brand-new music, a two player versus and cooperative duet mode via Ad-Hoc and other game modes not yet announced.
Obviously, there's no word on a US release; the game hasn't even been formally announced in Japan yet. US release or not, though, this is one UMD that's ending up in my collection as soon as humanly possible.
*Hoppas, hoppas!*