I would expect it to get some black accents á la iMac / MBA, and I would also expect them to look into H2O cooling.Quite honestly, I can't picture what would replace the current Mac Pro case or the MacBook Pro's case... I can't think of much to improve upon.
The Voodoo is already watercooled so there's no need for a chickenwire case, instead they can focus on keeping the noise to a minimum.
Me? No, I think they should start making computers again and stop obsessing with handheld gadgetry. Then again I know why they're holding off new computers at the moment, seeing as Intel has a new platform just around the corner. Those who are miffed about the lack of MB and MBP updates at WWDC would be even more miffed if they got new machines for this summer, only to find that they're updated with a spanking new Intel platform around christmas...You think apple should stop making computers?