Sony can be slowed down rather easy. MS could do it in the US, but international I think it will be Nintendo who slows Sony down.
If Nintendo can get the mature products out, that they have promised gamers, and keep them comin\' during this generation, all the while they cater to people with classic franchises like Zelda, Mario, Metriod then that could very well sell ALOT of units and slow Sony down. It is a given that Nintendo will be a huge success at launch, it is just a matter of how they deal with everything after launch.
Another factor, that could slow Sony down is the release of the HD. If it is a failure, I think alot of Sony fans will be upset, just like with the 32X or any other add-on situation.
In short; Sony probably won this generation. But that doesn\'t mean one company can\'t start the turn around for the next generation.