Honestly I'm not sure were, when and how linux gaming will be taken seriously. It's great to see companies like S2, id and others making great titles for linux but they are really a minority... It's hard and costly for the companies to target wide hardware range and at the same time different OS's. According to recent numbers only recently desktop linux usage reached 1% of the total market share... I hope this cenario changes quickly because I'm tired of dual-boot just because of gamming :P
One thing that really needs to appear are flexible, easy and powerfull frameworks to leaverage the work of dealing with portability. I know that there are great frameworks like OGRE and CS but I know from experience that they are no DX SDK by far.
Even little things like SMP are hardly perfect... Recently I worked with OpenMP and I must tell you that it's really hard to achieve the same efficiency when comparing to native hardcoded solutions...
Let's see how things evolve and maybe the current paradigm begins to change for better for the *nix world