MacRumors.com

ThinkSecret chimes in with a report that PowerBook revision development wrapped up earlier this month.

According to the rumor site, the upcoming upgrades are for the 15-inch and 17-inch PowerBook lines. The new machines should be running a minor revision to Mac OS X (Blackrider).

While no definitive date is provided, "later this week" is floated as an expectation.

Last week internet whispers predicted PowerBook updates in the pipeline, with expectations of a thinner 12", 1.33GHz top speeds and FW800 -- while a recent Page 2 note revealed near zero stock of 12" and 15" PowerBooks at Ingram Micro (a major distributor).

Update: Article updated with info about the 12" PowerBooks, which should arrive after the 15"/17" updates.