I've noticed one thing everybody keeps forgetting: Price. The X360 sold more, because it's always been about $100 cheaper.
If there's going to be a new generation of consoles they are of course going to cost more, but beyond more raw processing power/graphics there needs to be something else new hardware-wise to even think about for a next-gen console. The PS3 in 2012 will probably be $199, or $149(cheapest).
PS1 (CD-ROM), PS2 (DVD-ROM), PS3 (Blu-ray/1080p), PS4, my guess it will keep blu-ray and have the capability of reading "several" layers and read at 8x or faster.
I don't think this kind of technology will be available cheaply in 2012, I'm guessing 2013 at the earliest; Only because the cost would be too high, which is something consumers look at first when buying a game console, second would be the games that come with it, and third would be the consoles specs (if they even understand them--casual gamers).
X360 could very well have it's next gen in 2012, they would of course use the Blu-ray drive and the likes. But, remember "Price", if MS wants to have this better than the PS3, they are going to cost more than the PS3.