The 360 is coming up to 4 years old and has an 8.5 million lead on the PS3, the PS3 would have to start outselling it by a margin of approx 354k consoles a month for 24 consecutive months just to outsell it. The 360 is still pulling ahead of the PS3 and there is pretty much no way I can see of it overtaking the 360. The 360 has the bigger market and more games so when the prices reach the sweet spot the 360 will still sell well by virtue of it's strong library of games.
The truth is that it wont happen and I am also expecting Sony to be the first to pull out of this gen.