Having good developers using Windows will be a great boost for ecosystem, a percentage may choose to experiment with UWP, a react-native developer may try a Windows version of app.
Only thing to loose is people may not build cli tools for Windows, but that is already a lost cause. Linux won't pose a threat to GUI, so no chance of non developers getting comfortable and migrating to Linux. So win-win and later some more win.
The paths and base configuration will match your production environment, no worries about version mismatches or missing extensions. Ubuntu packages generally come with a sane and ready-to-run configuration, with service scripts and the like. (I use pkgsrc which seems more polished than Homebrew, but the installing experience is still not as nice as Ubuntu. Maybe someone will make a "Linux subsystem for Mac"...)
If anything this helps Linux because it cements popular Linux distros as the default *nix environments.
This can be done today on Windows too of course, even without this new fancy thing.
There are still a gazillion people using WAMP (and so on) as a bad impersonation of their production environment, so this fills a role.
Here's a question though that I seem to not see answered (but maybe I'm not reading enough):
Can I run MariaDB or nginx or other "servers" in this environment? Or does that stuff not work?
For any new programmers who want to learn more, search for "ANSI escape codes", VT100, "terminal emulation", termcap, and terminfo. Maybe add curses and pseudoterminal for extra credit.
Most "advanced" cloud services are built with the aim of locking you in (AWS, Oracle, Heroku, etc etc): easy to adopt and easy to extend, which means "hard to leave". Microsoft is no exception.
This microsoft are no longer the ridiculously dominant force they once were.
Linux is a core part of their cloud business now.
They have a new CEO, and a lot of time has passed.
They are actively trying to change a lot of their culture and approach to things.
I would love to see MS get their crap together, but it still seems like they can't break their addiction to abusive behavior.