Ever since Gabe Newell calling Windows 8 a "catastrophe" and their striving towards supporting a more open operating system like Linux, I have been feeling all too concerned about Steam for Windows shutting down permanently all because Valve hates Windows.
Now, I am a Linux user and I use it regularly, and I also have Steam on Linux (native), but with all of Valve's recent strides towards getting everyone to jump ship over to Linux, including ambitiously releasing Steam Machines with a Linux distro called "SteamOS" in which EVERYONE hated and considered Dead on Arrival for being too buggy and broken, even when compared to the Steam client for Windows, I am actually predicting that sometime by the end of next year, Valve will just turn off functionality for the Steam client on Windows altogether (and possibly Mac as well) and move ALL of their Steam-related assets over to Linux.
But what made me want to post this piece of concern is when I saw the comments on a post about Tim Sweeney of Epic Games predicting that "Microsoft will make Steam progressively worse and worse" and saw one highly-upvoted comment saying that even Phil Spencer (The head of the Xbox division at Microsoft) called bullcrap on that statement and Microsoft is actually doing the opposite of what Sweeney was predicting, and all of that "progressively worse and worse" activity was all Valve's responsibility just to get EVERYONE to jump ship over to Linux!
Therefore, my prediction is that when Valve says "We have been betrayed as a gaming community" and announces that they are turning off Steam for Windows permanently, so much backlash is going to happen. So many gamers will boycott Valve just for greenlighting that idea, Phil Spencer will plead with Valve not to shut down Steam for Windows. GOG will market on top of their DRM-free philosophy that they will NEVER drop Windows support and will encourage developers to jump ship from Steam over to GOG, and will add in a webpage showing Steam users what other platforms to get their games on, even if it only happens to be on console, and they will hold a sweepstakes where the winners will receive games of their choosing for free on non-Steam platforms.
I don't know what specifically would happen to Valve once they shut down Steam for Windows, but I think it's something to do with them losing too much money, but even then, they wouldn't care because money to them is less valuable than "freedom" and focusing all of their assets on freedom-focused operating systems.
TL;DR I don't know about you, but a lot of things Valve has been doing since Gaben calling Windows 8 a "catastrophe" has outright CONVINCED me that they will be shutting down Steam for Windows soon. And if they lose money from it, they will not care about it since money is less valuable than freedom to them.