The 360 sold 100k more units than the PS3 this week. Next week, things will get even better with the release of Last remnant in Japan. That could be an extra of 15k units in Japan (23k this week might be possible). So we have around 220k more Xbox360s than the PS3 in 2 weeks and the december hasn't even started. I think the Xbox360 could increase the gap to 6.5 million at the end of the year.
Well and I don't see why things should change (early) next year. Sony won't cut the price straight after Xmas, that would be stupid. So a price-cut might happen in March or April. That would give the 360 another 3-4 months of outselling the PS3. so let's say another 14 weeks for the 360 to sell better than PS3. Let's calculate with an average gap of 50k each week. That would be 700k more Xbox360s than PS3. The total gap would be like 7.2 million. We just don't know if Sony cuts the price, which would make get the PS3 even deeper in the reds, and we don't know how games like GoWIII or Killzone2 can affect console-sales either. So it is pure speculation so far.
But the really important thing is the software sales. That is, where the Xbox360 really starts to shine. Gears of War2 is insane, Fable did a great job, CoD WaW seems to do a goob job on the 360 (outselling the PS3-version in Europe), Fallout3 will cross 1million units soon, Left 4 Dead will be great and Banjo.... well, let's hope for legs 
PS3 on the other hand is good, but not impressive. LBP did okay, but didn't match expectations. It is bundled in Europe (with console) and in Japan (with controller), donÄt know about the US. So I expected to be a millionseller already. Resistance2 had a decent 1st week in the US, but nothing special at all. And it will be frontloaded like every other shooter. Socom didn't sell great (I know, downloads...) but a game bundled with a bluetooth headset and such sales is not good. Motorstorm just bombed.
If MS announces its Big Gun for 09 in February (like they did with GoW2), they might steal something of the hype for upcoming PS3 games. Great ingame footage of Alan Wake would make me happy :D