6 million gap (though will probably be nearer 7 million before end of the year)
Assuming Xbox 3 = November 2011
That gives us 3 years or 36 months for the PS3 to merely catch up.
For the PS3 to catch up in 12 months it needs to catch up 500,000 every single month, without fail.
For the PS3 to catch up in 24 months it needs to catch up 250,000 every single month, without fail.
For the PS3 to catch up in 24 months it needs to catch up 166,000 every single month, without fail.
500,000 starting in 6 weeks is entirely unfeasable and impossible.
250,000 means the PS3 needs to find a USA sized market to catch up by November 2010 and no such market exists.
166,000 is a touch more feasible figure, but still a very large (I don't think the PS3 managed that for a protracter period even when there was only a $50 difference) and definitely unsustainable for 36 months on the trot.
Therefore we can conclude, no matter what happens (bar Microsoft stopping production of the 360 for a protracted amount of time), PS3 is in 3rd place until the end of 2010.
It's chances are greater into 2011, but the longer into 2009 the PS3 is behind the less likely that will be.
Quite literally, PS3 needed to catch up a few months ago, but their fiscals have them bound.
It is important to note, however that the 360s recent price drop has caused surges in markets where it wasn't very strong (Japan, some parts of EU) and indeed the monthly gap has never been larger, its bigger then it was in 2007. So in fact the cheaper the 360 gets, (even if the PS3 drops also) the less Playstations branding will help them and so the gap will widen.