I strongly suggest you guys try porting to Linux, as many people use it, like myself. Expect much better performance from a Linux port of the game. If you do, my life will be complete!
Since they are upgrading to Dx11 I dont think would be easy to re-write the engine to OpenGL but I tottaly agree with you Linux for the win. Correct me if I`m wrong
Actually, they don't really need to completely rewrite the engine, just because they want to add OpenGL support, they just need to add OpenGL support and then make a Linux binary. I have no idea how their engine works or if it uses more Windows only libraries that also needs to be fixed for the Linux version. But they should anyhow port it over to OpenGL 4 to increase performance on Windows as well. Also keep in mind that DX9 is pretty much fully ported over to Linux through Wine.
BeamNG is portable middleware. The engine it runs on only recently began supporting Linux, and still needs a fair amount of work before any porting happens. Give this a read. http://www.garagegames.com/community/blogs/view/22988
