Various news outlets are reporting on upcoming Powerbook revisions.
The Register claims the new Titanium G4's will run at 600 and 700mhz:
Our source tells us the new PowerBooks are likely to appear towards the end of this month.
Of more interest is their speculation that "big" revisions will be expected at MacWorld Tokyo:
the new chip is simply being used to speed-bump the PowerBook before completely new models - described as a "big revision" - are launched next year at Macworld Expo Tokyo, the traditional venue of Apple's PowerBook announcements.