I think what you're trying to say is that the full rumbling of a new generation of systems doesn't start until there is actually some competition in the arena. It just happens that the market leader has been the last to market the last several generations. I would kindof agree with this point, but I would think it would be more accurate to say the next gen starts when the first new system hits, and that's what starts the decling of the old gen.
To put it in somewhat mathematical terms, cuz i'm weird like that, if each gen has a peak value of one, when machine A enters the fray, the "next gen" takes on a small, but present value, while the previous gen dies down a little. This happens even more so when the next system enters.
It's like one gen is growing while the other is decaying, they each have a maximum of one, however gen A + gen B is equal to one as well.
I think you're confusing people by not specifically stating the the next gen not really starting yet doesn't mean that no next gen systems are out yet. I think people are interpreting what you're saying as saying that X360 isn't next gen.