Also, if I recall correctly, the 360 sold about 9 million units in 2006, in 2007 they sold about 7 million, despite halo+price drop( I believe it is possible the numbers will be smaller still for 2008).
No, they shipped 9 and 7 million. They sold 7 and 8 million, which is an improvement, not a drop. You may not like it since it contradicts your theory, but the 360 had better retail numbers in 2007 than 2006 (in all 3 markets, even Japan!).
I just don't see the trend that you are claiming. Yes, the PS3 is trending up. But so is the 360.