OpenGL has a unique opportunity coming soon on the Windows platform. Microsoft has decided to use their coming DirectX 10 suite of APIs as a bullet item available only on Windows Vista, their next generation operating system. Rather than give their best effort to ensure acceptance of DirectX 10, which would mean making it available on all later versions of Windows, they are shooting it in the foot to help propel Windows Vista sales. This is where the opportunity lies.
Developers who would normally use DirectX on Windows will be thinking twice before targetting DirectX 10. Most publishers prefer to target as large a market as possible, to ensure as many sales as possible. To use DirectX 10 would mean limiting your market to only Windows Vista users. This would be unacceptable to most development studios, especially for the first year or two after Windows Vista’s release. There would simply be too few users. The market would be too small.
One possible solution for them would be to continue using DirectX 9. But this would mean giving up all the new features shipping with DirectX 10 compliant video cards. The resource virtualization, shader model 4.0, etc. would all be unavailable. Additionally, DirectX 9 and lower support are offered through a software layer on Windows Vista. (It is unclear at this time if this means a full software emulation or simply an additional layer of indirection.) This means decreased performance for DirectX 9 and lower titles on Windows Vista. This would be very unacceptable to most development studios.
What then would be the best solution? OpenGL will offer all the latest technology available on all the latest video cards. It will be available on all the latest Windows (and non-Windows) operating systems. If you use OpenGL you can target the largest market and use the latest technology; something that will simply not be possible using DirectX unless Microsoft changes their mind and makes version 10 available for Windows XP and earlier.
What this all means is that OpenGL has a brief window of opportunity to displace DirectX in the Windows application/game marketplace. OpenGL is far from dead. In fact, its greatest day may be very close.