The new G5 specs are amazing but I would say there is no chance of them coming to the iMac soon as the G5 enclosure is basically one big fan. The iMac is so tightly engineered they just couldn't do it in the short term.
My dilemma was an iMac 17" or a G5 1.6ghz. I have decided on the iMac. It has great specs and I am a home user doing things like gaming, listening to music and building my web page. Simply don't need the pro specs of the G5. I think the G5 will give a great boost to the iMac line as we once again have a clearly defined performance line between Pro use and consumer use.