Sources that can be qualified as reliable informed MacosXrumors that Apple is planning to revamp several lines of Macs (if not all) within early October and early December.

Powerbook, iBook, Mac mini, iMac, eMac and PowerMac lines will all be updated during the next eight weeks, according to the sources. The Mac mini’s update will probably be the first to go official. Last week, it has been rumoured that some 1.5Ghz versions of the Mac mini have already shipped. The xServes may also be updated during this period but sources show less certainty.

Additionally, sources told us that Apple plans to significantly drop pricing on its Cinema Displays. Today we can easily find high quality 20" TFT displays for about $599 and 23" for about $899, so we can speculate that the entry and mid-level’s new pricing will be close to this. Sources did not exclude an update on the Cinema Displays either.

Sources comment that Apple probably wants all its line of products to be attractive for the year-end holidays season.

UPDATE: MacBidouille also believes "there's something big coming", pointing out that there is very low stock on most of Apple's hardware product lines. The author explained us in a brief email discussion that this situation is really unusual, even during end of quarters.