Considering how much Valve are pushing more an more towards Linux and have even spoken out against things like Windows 8 stating they hate it, lol, and that various things like HL2, TF2, L4D (currently in beta), CS:S, and so on are being pushed to Linux now I think we'll be seeing the SDK's getting some much needed attention towards Linux lovers too hopefully.
I for one would totally love a GoldenEye: Source native Linux Client, am sick of having to play stuff via wine, hehe. And if after v4.3 goes opensource, hopefully that may make more developers help out (I'd certainly look at the code an try to help whenever I can, but my plates very full a lot of the time unfortunately with many other projects).