It could be established as a add on card, but only if games put it to good use and convince people that it's worth the additional cost. If for example GRAW with a physx card does not have significantly and noticeably improved physics over the xbox360 version then there would be no reason to buy a separate PPU - not only because it wont improve things much, but also because it would show that similar physics could be done with a multicore cpu. If, on the other hand, the PC version shows mind blowing physics unlike any console version, then it could convince me to buy a physx card. I'd rather not take away from the graphics power of a gpu to do physics, unless the graphics hardware was equipped with additional processing power to do physics calculations at no peformance cost on the graphics side.