This is Microsoft trying to Embrace, Extend, Extinguish Linux.

[This is] good for Linux enthusiasts not running Windows since the potential user base for Linux applications will become much larger.

What will probably happen is Windows will be able to run all Linux software, so there will be less incentive to switch to Linux. Programmers will be confused by thinking software they write in their Windows testing environment will run on all Linux distros, but there will inevitably be incompatibilities as Microsoft extends the capabilities of Linux software on Windows. Additionally, Windows native programs will run more efficiently, so developers will still not have an incentive to develop cross-platform for Linux.