No announcements about any other Mac models have been made (yet), but one of the team members did hint that some progress had been made by him on his own G4 Mac laptop. I can't remember if it was a PowerBook, or an iBook. Even though it would seem logical to port to other G4 Mac models, the Dev Team might have completely different plans for the future, or they may find that some of the G4 Mac models are more difficult to crack and complete a port to than the MacMini was. I would imagine that much of their time in the near future will be spent still working on improvements for the MacMini release, as it could probably still use some improvements and there are still missing drivers for some of the MacMini's hardware add-ons too.
Personally, I am hoping for a port to the G4 PowerBook's, as I would love to have a fast MorphOS laptop.