Dev's don't give a crap what they write for, in fact, a few I know hate D3D's lock in so it's not all roses. Same with Apple when Blizzard released Diablo 2 for it... how much of the market did they have circa 2000? Quote from wikipedia "Statistics from late 2003 indicate that Apple had 2.06"
Diablo was a AAA title, no doubt and regardless of what the statistics say I would imagine that there is at least as many if not WAY more Linux users now as Apple had in 2k3.
So what was your point again? It just takes faith and you have MICROSHAFT and CRAPPLE fudding their minds. They know it can be profitable their just being pansy's about it IMHO... Just say well we only support official NVIDIA/AMD/INTEL drivers then they will be right where they are on Windows. Assuming they use OPENGL from the get go, which doesn't happen much.