The unfortunate thing for the PS3 lasting past the begining of the next generation is that it is easier to design a cost effective product from scratch than it is to reduce the price of the product. We're already past the point in the generation where a company could release a more powerful gaming system than either the PS3 or XBox 360 and sell it for $300 without losing money; and as time goes on the potential "next generation" system will become less expensive and more powerful, and by 2012 the gap between the capabilities of current consoles and next generation consoles will be large.
Now, I think what plays the biggest role on the long term health of both the PS3 and XBox 360 is the fact that they're "Tied Together" and 90% of all games released for one platform are released for the other. If this continues for the next couple of years (which seems likely) and one/both of the HD consoles is replaced, it is likely that both the XBox 360 and PS3 will face a pretty large blow to their support and their ability to survive past 2012
