It's not like Windows Server is going away, it's still good at many things a small to mid-sized corporation may need, like Active Directory to manage users and policies, file servers, print servers, network policy servers and the like. Linux can do all that, but its so much worse to setup and manage. However, for things such as running web applications and cloud workloads Linux is pretty much the standard nowadays, mostly thanks to docker. For the desktop users both work and I still rather manage a business with Windows PCs for my users than Linux. I just wish Windows 10 didn't have so much crap with it, I might use it for a workstation then.