The new GPUs should, hopefully, cost abouts the same as what they are now. Keep your fingers crossed
I am not sure if CUDA cores can be utilized for editing in SLI form, or if it limits to just a single card. Hmmmm.
Anyway, I say wait to Ivy Bridge, by then the newer nVidia cards should be out, or close to coming out. Prices will drop on the current generation, and maybe the 460 again (if they don't stop selling them first).
You could always just go three way with Ivy Bridge and three 460s. Older cards don't have to stay on older platforms =P