That is true, if they could get it ready for September it would be different, but as it is, it is Spring, so at best it would have come in November, and yeah that is certainly busy. I don't think there is any danger of it coinciding with XIII, I doubt that will be out until Winter 2010...
In terms of the life-spans of the consoles, I am pretty sure that we will see the nextbox in 2012, 7 years is a long time to keep a console on the market, and I assume M$ will want to beat the competition out the door again. I would be interested in knowing how much the Xbox 360 costs to make, because if they are near breaking even with the arcade, it is so cheap that they can keep it at that price for a long time and probably get some decent money from it, especially if this generation does keep on going for ages as then they will get even greater software sales







