The last 4 months for each console should sell roughly the same number of units as it did in the first 8 months.
Actually I was including Wii and DS in that, which skews it because they sell well through the year and don't have supply for huge Christmas sales.
So for a PS3/360 comparison HappySquirrel is correct... around half the years sales will be in the last 3 months.
So assuming weekly sales stay similar, in the next 1.5 months (6 weeks) PS3 should sell ~700k and X360 around 550k
That would put the totals for the first 9 months at 6.7million PS3s and 5.0 million X360s
So the rest of the year will probably reflect that with a further 6.5-7.0 million for PS3, and a further 5.0-6.0 million for X360 (having a price cut will boost it a bit)
So PS3 should close the gap another 0.7 - 2.2 million (likely somewhere in the middle)
