The rumour mill is spinning rather quickly lately, with rumours about Microsoft apparently looking at buying Valve, EA and others.
Polygon cites a "reliable source" for this information:
Some of the names being thrown around as possible acquisitions by Microsoft are, frankly, astounding, even unthinkable. But the fact that they are doing the rounds is instructive. The most recent one we heard (from a reliable source close to Microsoft) was, in fact, Electronic Arts. We also heard a whisper about Valve and about Korean outfit PUBG Corp., which Microsoft last year signed to a timed exclusive for its hit survival shooter, PlayerUnknown’s Battlegrounds.
Considering Valve has a majority grip on the PC gaming market, constant growth and quite likely more money than they know what to do with, it would obviously be a target for Microsoft. However, to me, those are also all reasons why it just wouldn't happen. On top of that, Valve is privately owned and I doubt Gabe Newell will suddenly give it all over to Microsoft.
Let's not forget how Valve has also been paying people to improve Linux gaming. Valve has people working on SDL, Mesa, SteamOS (multiple updates this year already), Virtual Reality and plenty more towards making Linux a more attractive gaming platform. There's also this recent interview with Timothee Besset from our friends at BoilingSteam which gives a little glimpse into the work Valve is doing behind the scenes for Linux gaming too. It also seems from that, the Linux port of Street Fighter V is not actually dead. It seems they have a habit of announcing things too early!
Obviously if Microsoft somehow convinced Gabe and co to sell up, Linux gaming would change significantly, but I'm telling you now—it just won't happen.