I actually do use Linux as a Desktop PC at home. This is more of a hangover from when I was living at my parents for an interim period and wanted a PC I could use as a media centre. I bought myself a little NUC PC, fitted it to the back of a TV, and installed Ubuntu on it. I didn't want to "fork out" for Windows as it seem pointless for what I wanted it for; which was more of a device to be able to run streaming services on and play any personal videos I had as well.
After I moved back out I rebuilt the PC with a more desktop use in mind; I still had my old Windows 7 PC (which had been in storage), but like I said it was old and struggling so I took the time to learn how to use the Ubuntu. I really enjoyed it, and haven't really gone back to Windows (at home since)
Since then I have 2 3B+ Pis that are running OpenLDAP and I'm trying (so far without success) to get an AD properly up and running. Something i'm looking forward to as SQL Server 2019 supports OpenLDAP and will likely be of great benefit once I (or likely someone far more clever than I) documents the process end to end.
I finally got around to building a new desktop in June and I stuck to Ubuntu again; this time using the Kubuntu build. I must say that KDE Plasma is a really nice working environment. I use it is a home PC but also spin up containers (using LXD) all the time; it's so good for sandboxing.
Will Linux take over Windows for the home environment? No, I doubt it. Gaming is a huge industry on Windows, and although Steam supports Ubuntu (that almost went out the window a couple of weeks ago) many other providers don't; and not every windows game runs (well) on Ubuntu.
From a SQL Server perspective I still really miss SSMS on Ubuntu; and I wish it was available. ADS is a poor replacement for it. There';s still a lot of functionality on SQL Server on Linux that's missing, and I doubt we'll see those for a few more versions.
From just a Server itself point of view though, yeah, I can see more things using it. The Linux environments, especially those containerised and when running without a GUI, are very lightweight meaning that what ever is running on it has less contention for resources. i think it'll be a while before we see movements from big Microsoft users to Linux distros. Maybe if/when "easy" AD comes, like EdVassie mentioned, that'll help people move across.
Excuse my typos and sometimes awful grammar. My fingers work faster than my brain does.