Yeah, maybe in late 2010 we'll see a big PS3 game run it's shaders on the Cell instead of the GPU (something like God of War 4 probably). But in those days all the talk will be about the Xbox 3 and PS4.
Until then the graphics battle on next gen will be all about GPU only, and you know very well that the X360's GPU is at least as good as the RSX in the PS3.