this is the reason why i predict that the powermac will be the last computer to go to intel while the powerbook ibook emac and imac are the first in lines. Especially the powerbook and ibooks. But I honestly think that they wont realse the intel chip into the Powermac till late 2007 or really 2008 as the G5 is a very good c hip. But its time to change; hey did you see the new g5 chips how the consume 100watts!!!!!!! This is exactly what apple was talking about, that intel is going to provide apple with less watts allowing for a cooler operation. IT will also have a hughe cost impact on the g5 as it wont need 9 fans and a water cooling solution! IT just needs one fan or 2 and it will be still quiter then the g5 now as they have BTX tech which is much quiter than any g5 right now.
personally i think the quad processors are able to hold on for a REALLY long time... before intel comes out with something powerful enough to topple over that...