I've done some maths for older games on the PS3 which could possibly still reach a million units sold. (even if it's quite unlikely)
Mortal Kombat vs DC Universe
968,789 sold
31,211 left
~2,200/week --> 14 weeks --> million seller in February 2010
SOCOM: Confrontation
911,001 sold
88,999 left
~4,500/week --> 20 weeks --> million seller in April 2010
Tomb Raider: Underworld
944,883 sold
55,117 left
~2,000/week --> 28 weeks --> million seller in June 2010
MotorStorm: Pacific Rift
788,443 sold
211,557 left
~5,000/week --> 42 weeks --> million seller in September 2010
[according to VGChartz data]
These calculations are of course completely based on the assumption that these games will continue selling as much as the have during the last few weeks. What do you think?
By the way, thanks for this great thread! :)