Releasing first is overrated, especially in Sony's case. I say that because they would still support and market the PS3. If the Microsoft 720 came out, the PS3 would still sell decently against it at a sub-$200 price point.
People forget that sales are a marathon, not a sprint. You measure a staggered race after both competitors have finished, not after one finishes. The PS3 is going to finish this generation nearly tied with the 360 for total units sold, and with a larger installed base. The important lesson Sony should take away from this generation isn't to release first, but to not screw up your launch.
Now, keep in mind, though I said "in Sony's case", I think the same could be true for Microsoft, but that's assuming that they don't support the 360 after the 720 launches.