Appleinsider is reporting that reliable sources are pointing towards the release of revised PowerBooks.
Although the article describes the update as a mere 30MHz for the 15 and 17 inch it goes on to describe the new PowerBooks to include DDR2 SDRAM and for the two higher models to gain HD resolution screens.
This rumour first surfaced in February with the last revision of PowerBooks where Apple accidently shipped a manual that mentioned 1920 x 1200 pixel resolutions.
The new PowerBooks are expected to be released at Apple Expo in later September.