In the long run, Canonical might have been the trojan horse Microsoft needed to demolish Linux from within.
As developers, we're all enthusiasts of the WSL and how we don't need to dual boot, run VMs etc. any more. But in the process, we may end up giving less love to our once beloved DEs. This in turn creates a negative feedback for Linux desktop adoption. Also, less bare-metal installs means less bugs discovered and ironed out in the kernel too, less incentives for developers to release drivers, etc. so in the long run it's going to hurt Linux much more.
This can go the other way as well. If developers can target WSL and run on both Linux and Windows it increases their user base. This could end up making it easier for users to move away from Windows since one of the big hurdles is software compatibility.
If it is a Trojan horse, it does seem to be a partnered one that works both ways. WSL is the easiest "Hey Developers, Try Ubuntu" experience Canonical could hope for. No virtual machines to wrestle, no boot CDs to awkwardly try to boot on machines that no longer have CD-ROMs: push a couple buttons, install an app.
As developers, we're all enthusiasts of the WSL and how we don't need to dual boot, run VMs etc. any more. But in the process, we may end up giving less love to our once beloved DEs. This in turn creates a negative feedback for Linux desktop adoption. Also, less bare-metal installs means less bugs discovered and ironed out in the kernel too, less incentives for developers to release drivers, etc. so in the long run it's going to hurt Linux much more.