Well if it has taken 11 months to get 1m back for the PS3 then it is going to be a long time. For the PS3 to over-take the 360 by the end of 2009 means the PS3 has to sell 500k a month and the 360 not sell anything. Now seeing as these are the numbers for the past 3 months
Sept = PS3:232k. 360:347k Wii:667k
Aug = PS3:185k. 360:195k Wii:453k
July = PS3:225k 360:205k Wii:555k
It would seem quite silly to think the PS3 out of nowhere will go on to post Wii type numbers. That is not going to happen. So to expect the PS3 to outsell the 360 by the end of 2009 is fantasy land stuff.
So then lets assume the PS3 stays at its average of 200k a month. 200 x 24 months (2 years) = 4.8m. Meaning that by the end of 2010 at it's current ratio the PS3 could make up 4.8m units if the 360 does not sell 1 unit. Again not very likely.
So my prediction is that IF the PS3 can increase sales and not decrease sales then it has a chance for 2011 to overtake the 360. However i just can't see it happening. So i predict never.