The 360 is selling software like crazy. What does that mean? Developers will, for the most part, continue developing software for it unless owners stop buying it. By the time the PS3 has a commanding lead (assuming we reach that point), there will likely be 35-40 million 360 consoles in circulation. If developers can sell 1M+ copies of a particular title with less than a 20 million userbase, you can be sure they will continue to develop multi-platform titles for a long time coming given that 2+ million first week sales for blockbuster titles won't be out of the question. It really is as simple as that.