Yeah, if only it was possible at this time lol. I can't wait for the day when raytracing is as common as bump mapping *drifts off into a daydream*
Well, having in mind this:
The OptiX engine runs entirely on the NVIDIA CUDA compute architecture, with its performance scaling linearly as the number of CUDA cores increase within the GPU. The latest "Fermi" class GPUs deliver between 2-4 times the performance over previous GT200 generation GPUs, which in turn are 3 to 4 times faster than the G80 generation of GPUs.
...and doing some maths:
9xxx: 1-7 fps.
GT2xx: 1 or 7x3 or 4 : 3 fps (at worst), 28 fps (at best).
GTX 4xx: 3 or 28x2 or 4: 6 fps (at worst), 112 fps (at best).
GTX 5xx: Slightly better than the GTX 4xx. (7 fps at worst, 120 fps (or so) at best).
Well, that having in mind that the base is my old, crappy 9600GT, and that's in default windowed mode, but the progression seems promising, isn't it? I'd say that in abouuuut.......3 or 4 GPU generations it could be possible
EDIT: Fixed "worst" numbers, due to a error in the first one that mistook all upper proccess.