Hmm PS3 has sold 4 million more then 360 had last year.

[Steroid]

Looking at VGchartz, 360 had 21.5 million units sold this time last year (it's 3rd year on the market) and PS3 has 25.5 currently (its third year on the market). So considering this data I would say that the PS3 outselling the 360 isn't just "possible" but likely.