One of Id Software's Co-founders, John Carmack, has stated in a post on Reddit that porting games to Linux barely makes into his top ten priorities. He states that a good business case cannot be made for officially supporting the operating system and drivers.
He stated that he was happy that their game RAGE ran under Wine, but that no special effort was made to support it. He also said that he would be surprised if parent company Zenimax showed any interest in publishing and supporting such titles.
I can't speak for the executives at Zenimax, but they don't even publish Mac titles (they partner with Aspyr), so I would be stunned if they showed an interest in officially publishing and supporting a Linux title. A port could be up and running in a week or two, but there is so much work to do beyond that for official support. The conventional wisdom is that native Linux games are not a good market. Id Software tested the conventional wisdom twice, with Quake Arena and Quake Live. The conventional wisdom proved correct. Arguments can be made that neither one was an optimal test case, but they were honest tries.
He goes on to say that it would be better to run games on some kind of emulation on Linux that to have to refactor and rewrite everything in native code, and that a set of best practices would allow developers to create Linux versions with a lot less problems and effort. He stated that if "Properly evangelized, with Steam as a monetized distribution platform, this is a plausible path forward."