Id point out that DX10 was gimped from the beginning, as nVidias DX10 cards werent totally compliant with the original DX10, thus later we had DX10.1.
That, the fact it went away from the norm, meaning we needed a new operating system, going against a OS thatd been around twice as long as any prior to it, the poor reception to Vista etc slowed the uptake of DX10/10.1 into the market.
Now, were back on track, with windows 8 set to release in 2012, or the common 3 years between OS'