Two things I'm wondering about.
First: The 360 is becoming increasingly less feasible of a platform in Japan. I know many Japanese developers are trying to appeal more to the western market, however, they are still not going to neglect their home territory, and there are still many affluential Japanese developers / publishers. As the gap continues to increase there, I see less support from these developers for the 360. And yes I am aware that 360 is ahead in America, however, it is not a 3:1 difference, ps3 will still remain a viable platform in America.
Second: 360's success lies majorly in the fact that it is perceived to be the cheaper choice. I know it is a long way's off, but what happens when the 360 drops to $99 dollar range. How do you price cut from that to increase sales. At that point ps3 will be at $200 likely, and will still have some room to go. However, this will only take effect once this generation is pretty much over.
My conclusion is that ps3 will eventually win because of these two factors, however, it is a long ways off and won't really matter too much.