You know, you raise an interesting point. I remember last year there was a rumour about a completely new Mac product being introduced. Maybe it could actually happen this time.
Not that I agree with Cook, but it's clear that SJ was adamant against an xMac and its cannibalizing potential, as well as its expandability (always a pet peeve for SJ).
Tim Cook has none of these prejudices as well as limited long-term vision compared to SJ - therefore, the xMac is finally coming.