If OpenGL wasn't caught between the past with old CAD software running on graphics workstations and a lack of investment in the future then sure, it would be a viable alternative. The recent release of OpenGL 3 wasn't taken with much enthusiasm from the development community.
As far as providing competition to Direct X its still a bit of a joke really. We have a better bet in getting OpenCL taken as a standard so let OpenGL die and have OpenCL take its place. The fact that OpenCL works on a wide range of platforms and is actually supported wholeheartedly by Nvidia, AMD, Intel and Apple means that the platform has a pretty decent shot at success.