By best guess would be that both consoles are already maxxed out from a graphics point of view.
The video cards on both the 360 and PS3 from a raw graphics processing point of view aren't too far off from each other, so really the only difference in terms of remaining power would be the CPU.
Most gaming PC's are only running dual core processors (where as the 360 has 3 cores, the PS3 has 7), yet can blow both consoles out of the water in terms of graphics. Why? because the graphics cards in PC's are far superior.
So yes, the PS3 has more CPU processing power, but from a graphics point of view, it really can't do more than a 360. In the future I expect to see the PS3 pull ahead in respect to the scale of the games it provides, with larger environments, possibly greater levels of physics or computer AI, but the graphics will still be comparable on both.