Earlier in the thread you made a comment about how poor IW sales will kill the franchise. Thief 1 and 2 both sold poorly and yet we still have another sequel coming.
Thief was a small to moderate budget game, and Thief 2, which used pretty much the same engine and a majority of the same resources, was definately low budget to produce. These types of games don't need to sell well.
On the other hand, DX:IW & Thief: GenericXBOXName are big budget games which need to sell big numbers. DX is clearly an unmitigated disaster and if Thief doesn't sell well as well there will be repercussions