This really shows the necessity of staying on top of your game after releasing the console and not sitting back and resting on your laurels. Early on, the 360 sold well and above what the PS3 did, and yet the PS3 managed to come out on top in the end. Quite impressive.
Sony is going to have to remember this if the PS4 starts off better than the Xbox One. If they don't keep their game up, the Xbox One could surpass them eventually, just as they did themselves to the 360.