Edge? Pah, what about SQL moving to Linux a year ago?
First off, I think SQL being ported to Linux is far bigger than Edge which had pretty much already been done as part of Chomium.
If Windows were to be subsumed in to Linux as is stated I would see it more likely that Microsoft would do their own Distro of Linux with their own Desktop, as they have done with Chromium where they removed all the Google services and refernces and moved these to MS ones.
They are facing a big problem with their kernal, there is a lot of legacy nonesense in there. Moving to the Linux kernal and wrapping it in a Microsoft desktop with a built in emulation layer for "legacy" Apps in the same way Apple did when it changed from OS9 to OSX, would make some sense.
They have already done this to a lesser extent with Android with the MS Launcher you can get, they are limited to what they can do there by access to the Google Play Store which requires Google services to be installed. Being the dominant/monoploy phone OS and the way the iPhone litgation is going would MS support legal action to remove that requirement? And the an MS distro of Android with MS services wrapped up would be very appealing.
MS is all about selling services now, anything that advances that makes them money, owning the core desktop OS is not a thing for them anymore. Server OS is a little more complicated but needs a reduced feature set and can be a much simpler thing to support, you only have to look at the Nano edition to see where that can go. AD and such like are big things to move as well. But as I have said SQL is already over the fence.
The big thing to watch for would be a Linux version of Office, once that is in place an MS Linux desktop distro would not be far behind. The other biggie would be XBox moving over in the next version due around 2025-7.