Just been thinking about this and whenever I had a console for Christmas as a kid, the system would have already been out a year because in Europe consoles are always released in the new year.
Now there is no way Nintendo's new rig or the PlayStation3 will be out before Christmas in Europe, so if the XBox2 is, then Microsoft will have a huge marketing advantage, as it will be the only next gen console available for purchase in time for Christmas and the only next gen console the anybody can have on their Christmas lists.