Separating desktops and servers (which in this case is quite relevant):
Servers can be Windows / Linux / etc. and it doesn't really matter. if I wanted windows, I'd spoool up a windows VM. If I wanted a Linux server, i'd spool up a Linux server instance in a VM. I ONLY WANT Windows/Linux because of the applications that run on them. Server dev environment choice in that respect don't really matter unless you're deeply entrenched in a given vendor's server API stack. I've personally never seen companies do anything OS-specific services outside of a few DCOM based components like 15 years ago. If you have customers that want your server offering, they'll spool up whatever OS/hardware necessary to run it.
For desktops, this certainly matters a lot, since most consumers don't have multiple desktop OS's unless you're dancing with tablets/phone OS's as well. All that said, I see little interest for 'windows apps' or 'Linux Apps', 'Mac Apps', etc.. The web has really gutted the native platform applications market. Never eliminated obviously, but significantly maimed in the consumer space.
Lastly, desktop applications for Enterprise are generally still thriving, and .Net/Java/C++/etc.. zealots in companies still fight tooth and nail for the next project.