I'm not too worried. This is not a full Linux software stack, so it seems more useful to make Windows a more attractive development platform, but what you develop on this would still be
for Linux and not instead of Linux.
It might in theory tempt developers to migrate from Linux to Windows more comfortably, with both userlands now available at once, but this doesn't really attempt to make that process easier, other than that.
Besides, I don't feel like Windows is a that attractive platform to develop for nowadays with the cesspool that is Windows Store, the pointless new Universal Windows Platform when your apps need to follow a weakest link due to an almost non-existing Windows Phone market, combined with their lack of leading position on the web.
I think all this is what's bothering Microsoft, because with no development steam, the whole platform suffers a lot. I think the transition at Microsoft lately is happening because they are transitioning from a comfortable leader to a competitor, not because they are trying to squash the competition. They probably long for the days when they were in a position to still have that luxury.