Well....
The iMac having DDR2 and PCI-Express Graphics does kinda put a dampner on the PowerMac specs. While DDR2 was no doubt used in the iMac just for the fact that its lower power consumption - It wouldnt be needed in the PowerMac. I mean the performance gain surley wouldnt exist unless the bus speeds become a lot higher.... they could add PCI-express and Dual Cores then.
I could see the PowerMac's becoming a little smaller, and Apple replacing Dual CPU's with single Dual Core PPC's - then adding PCI-express.
Actually the PowerMac does support PCI-X which i guess might offset the 'look' next to the iMac. Thing is Apple will need something to make PCI-express worthwhile. No good if there are no graphics cards out there to make use of it ( i mean ones compatible with Apple systems btw) or anything else for that matter (which there isnt since no mac has PCI-E yet).