One of the aspects of this that I find interesting is the play that mobile devices will have on this long time battle. Apparently, DirectX is not coming to Windows Mobile 7 and with Apple trumpeting how you can build applications for the iPad and for the iPhone using the same "API", no DirectX on a mobile device seems like a mistake. OpenGL however, is implemented in Windows Mobile 6.* and will be part of 7.* so OpenGL seems to have been given another lease on life in the world of mobile 3D games.
Will they take advantage of it? If they don't Microsoft will make sure DirectX is on a mobile platform so that their games on Windows Phones can compete with the games on the iPhone.