It appears as though appleinsider might be wrong - http://www.thinksecret.com/news/0706imacwwdc.html.
Cool, I'd be alright with that! I am planning on replacing my G4 iMac in the near future, but my first priority is buying a new MacBook Pro. I think regardless of whether this rumor is true or not, I will hold off buying the new iMac until Leopard is released, and even then perhaps wait for a slight upgrade to the new iMac if it is indeed released next week, as I would expect a marginal speed bump if nothing else 4-5 months later once Leopard is released and shipping pre-installed on all new Macs.