I think it'll slowly keep on moving forward.

I'm not sure if it'll ever get a high popularity rate because OSX and Windows are focusing on marketing schemes which attracts the public.
Sure thing is that we'll get more graphic and driver support due to Steam.
The future also depends on the trends, what we'll want to have. If, for example, a brand new technology that everyone wants to get is purely GNU/Linux based (unlike ChromeOS and Android) then it'll open a lot of opportunities for the community.