G5 in a 'book, unlikely. Still, can't blame Apple for choosing to go with Asustek. I have several motherboards/pc components from them and they have all been great. The next 'book updrade will likely feature faster G4s, hopefully new video cards, DDR-II?, HD LCDs, SATA HDs (unlikely, but would be nice), etc..
Then we can look forward to 'books equipped with a Pentium M processor.