I don't think the 8 series will have it, maybe the later 9 series. They just made the purchase, and they've probably already manufactured the first 9 series cards the 9800 and the 9600. We might even have to wait till the 10 series cards are around to see support.
Anyways, they represent Physics processors, in hardware form. Like sound cards, dedicated and onboard, the difference mainly lies in the ability to take the load of crunching physics off the CPU or GPUs plate, creating a situation where the CPU has more leeway, resulting in better frames. The difference in quality between software physics processor, like the one in Crysis, and hardware processors, Physx, is arguable. Of course the guys at Physx will claim they do it better, whatever. The guys who created the software physics of Crysis claimed it was better than if they'd had used Physx's proprietary system. Either way, hardware Physics processors are somewhat uneeded, in my opinion, and as of right now. It would be kinda cool to get support on a GPGPU, general purpose GPU, which is to say a graphics card that is capable of acting as a surrogate CPU, able to make use of it's mighty FPU count and stream processors for all other processes, rather than just games. It would expand the repertoire of the thing, and in a good way