Just to remind you - the Power Mac G5 died as the Mac Pro replaced it way back in 2006, and in early January 2008, Apple introduced the 3.2 GHz, dual quad-core Intel Xeon (Harpertown 45nm)-based Mac Pro to become its most powerful machine to date. A lot has happened in the year that passed since then, and now the almighty 8-core Mac Pro doesn't seem that powerful anymore. The logical consequence of this fact is that, pretty soon, Apple should come up with a new Mac Pro.
As you can see in the image here, a new Mac Pro design already made it to the Web, although this is more like a concept based on various rumors, than the real thing. Speaking for myself, I would really like to see a tray loading optical drive, instead of the slot loading ones Apple has been using so far. Enough to say that I hate dust, and you will get the idea...
At last, I think Apple should be careful with the pricing and additional options. Maybe they could go as far as offering a black version?(that would really rule!) Anyway, if you want to see more pictures of this pretty cool design concept, take a look at the new Mac Pro here.