Two words for you Carmack: Steam Box
If Valve wants to bring their distribution center to consoles (and other devices) they're going to need a solid OS with lots of support, and they're going to need to run their games natively. With Valve and Unity (and others) starting to push for Linux support, more games will be ported, and GPU driver vendors will have more incentive to support the platform more in-turn. Using Wine is perfectly fine. If it runs good, it runs good, but that's never going to be the case in all situations with Wine unless more support is given to the whole systems, so at that point it's better to just support thing more directly (natively).
Besides, porting to Linux isn't even hard to do. Even if you're engine is directly using Direct3D calls (which is big mistake in today's multi-platform environment), it's easy enough to wrap OpenGL calls up a neat little DirectX box as a drop-in replacement (same for the other APIs). With Steam on Linux and more major Game Engines gaining Linux support developers will starting see Linux as another real source of revenue.