the macworld expos have lately been about 'i'-products like the iPod or the iMac, as well as about software introductions. 'power' hardware however, as well as the iBooks, have been introduced inbetween.
rumours are that new powerbooks should arrive by the end of october. however, these are rumours, don't forget that. but the DVI models have been around for quite a long time, so it certainly makes no sense to update them right now.
my sources tell me that apple is in the final testing stages of the new powerbooks - and that it's all about what processors will appear. apparently, the new iBooks are set to be released as either 700 and 800 MHz models or 800 and 900 MHz models, but they're depending on whether the G4 to be used in the new TiBooks will be available in large enough quantities at 1022 MHz. if the Ti's will use 867 and 933 MHz processors instead, the iBooks are going to be released at 700 and 800 MHz.
BUT the goal is to release both new lines by the end of October.