The minimal PS3/360 gap will be 3.5M and maximal 5.5M by the end of 2009

[Seihyouken]

It's interesting to note that in two months PS3 has taken the highest lead in worldwide install base 360 had on it (8,161,690 as of 08/30/09) and reduced it by exactly 20% down to 6,761,000.