According to Gamespot, it's developed by Arika and its release date is To Be Announced for Japan. Has anyone heard anything else about this title?
It's probably for the better too.. as much as I would love a portable TGM, I can't imagine playing one on the (atrocious) PSP d-pad. For the record, Mihara didn't even mention it when he listed various TGM versions and prototypes in his blog. Makes me believe it wasn't even that far into development.