The point is, currently, PPU's aren't needed. Your GPU and CPU can handle it. It would be GREAT if games utilized a PPU and even an AIPU (For AI) as much as a GPU and CPU. Think of the games we could have, fully distructable scenery, and AI that is smarter than you, as well as great graphics.

But realistically.... It's not going to happen, i doubt ever. With hardware becoming more and more "all inclusive", I wouldn't be surprised if you get PPU's in GPU's soon enough (as i said, the 2900XT is capable a physics processing.)