I think most would say that the xbox's life was shorter then it should have been. Microsoft was to quick to abandon the console even though games weren't yet pushing the system to it's limits. Well it would seem that Microsoft has learned from it's past mistakes as this statement from Microsoft games division CFO Mindy Mount shows.
"Look at the PS2; they've gone a long-time and seem to have pretty good legs on what they are doing...If we were able to do that, as CFO I think that's great, because every year you draw it out you increase profitability."
So it would seem we can expect the 360 to stick around a bit longer then the 1st Xbox did.