If they feel like it...
Legit Reviews has written up an article that reports on a presentation given by Standford's Folding@home professor, Mr. Vijay Pande. During the presentation Mr. pande announced that Nvidia's graphics cards will soon be able to fold for the cause along side ATI's graphics cards and Sony's PlayStation 3s. Apparently there are 70 million Nvidia cards out there in people's machines. If the owners of all those cards decided to run Folding@home, the amount of computing power being used would increase from 1.9 petaFLOPS to 7,001.9 petaFLOPS.
The launch date of the Nvidia Folding@home client has not been announced yet.
For more information on GPU and PS3 folding please check out the Folding@home Wiki page.