An anonymous/unverified report claims that Apple has already been seeded sample 90nm PowerPC 970s this month. Reportedly, they run from 1.8GHz to 3.2GHz and heat production is significant improved, with a 2GHz at only 34W, down from 57W. The 3.2GHz chip reportedly at 71W.
Target volume production for 90nm is reported to be in Q2 of 2004. Heat considerations are still a major issue for the upcoming PowerBook and dual G4's are still considered a possibility.