Always the optimist.......
Well, my laziness claim was based on Apple's past behavior with the older Xeons that came out, and Apple actually had them earlier than everyone else.
Also, considering the fact that they have never offered the latest and greatest video cards, that the likely mid-range candidate would be the ATI 5870XT. The low offering I imagine would be something nVidia related, and perhaps the high-end would be one of the new FireGL's.
If they are waiting for volume availability of the nVidia 480's, I would be most disappointed. Their performance isn't much higher than that of the 5870, and the power draw and thermal profile is off the scales.