To a degree if demand for Linux support was loud enough, they could probably swing a mandate to add support to both. I'm not sure if it'll ever get there but one example is that Valve is now aggressively investing in tools to enable playing existing Windows games on Linux. This could result in more happy Linux users asking for improved compatibility or direct Linux ports (for a better experience), but we'll see...
We produce our own game launcher (think: uplay or origin) and I asked if there were plans to produce a Linux version of the launcher. They replied “no because productions (games) [weren’t] asking for it.”
Inversely, when I ask productions if they will support Linux they say that there’s no point because the launcher doesn't support it and the launcher is mandatory.