Will the Lack of DX10 on XP Spur OpenGL Dev?

Sparr0 asks: "Microsoft has announcement that DirectX 10 will not be released for Windows XP (which means no Shader Model 4.0 and no Geometry Shaders). I have since been waiting for news of game developers switching to OpenGL, in order to get the best graphics on the best hardware on the most popular gaming OS, however there is nary a whisper of such. Will such a shift occur, even if only in small amounts? When? Why not? It is probably safe to say that Unreal Tournament 3 (AKA UT2007) will have OpenGL as an option in Windows, but that is both unsurprising and also a long way off. Ditto for Quake Wars, and most other games that are planning a native Linux clients. Where are all of the other big names with Windows-only offerings? Why haven't we heard from Valve, Blizzard, Sony, or EA, to name a few?"