The only trend I'm seeing is that they are open-sourcing stuff they don't care about anymore. E.g. I just tried OneDrive, which has a shitty implementation on OS X and no implementation on Linux. If OneDrive doesn't have a Linux client (or good OS X support), what chances do you think Edge has?
And forget about Linux - if extensions are going to get distributed through the Windows Store, as this article claims, you can say goodbye to OS X support as well.
As far as I perceive it, they're open sourcing dev-facing stuff, allowing you to create stuff for Windows without using Windows yourself. Which is a refreshing change.
Along those lines, you might expect them to make a Linux version of the Edge browser, except that it won't be the exact browser the majority of users will be running - I suspect they'd point you to the VM images they already have at modern.ie instead.
I wouldn't be so sure. Microsoft has lots of technologies that they dropped, including VB6, COM+, DCOM, DAO, ADO, ActiveX, Silverlight, WPF, WinForms, XNA, IronRuby, IronPython and the list is probably much bigger. I couldn't help but mention the Iron languages. Microsoft halted development right after open-sourcing them. And now they are effectively dead. Well no, open-source never really dies and those projects are just waiting to be adopted - which is the great advantage of open-source. But we are talking about Microsoft and their interests here.
Is it that much of a stretch to say that Microsoft is obsoleting .NET? Given the moves in "modern Windows" and WinRT, with their focus on HTML5 and the revived interest in C++, plus killing Silverlight / WPF which was the hot new thing only 6 years ago, well, it doesn't look good.
Then you're not following Microsoft enough. They are gradually making all the development tools cross-platform, just to bank on the dev knowledge of the users of Windows, Linux and Mac. Browser add-ons is another area they can get benefitted from by the help of other platform developers.
They have made .Net & CoreCLR open source (including the compiler, runtime and libraries), enabled Visual Studio to do more than developing just Windows applications (they now allow developing Android/iOS apps as well) and are trying to make developing for other platforms even easier with VS 2015.
Not only that, they just released a cross platform Code Editor which works on Windows, Linux and Mac, called 'Visual Studio Code'. That and more was announced in the Build Conference held recently.
Visual Studio Code is just a re-branded Atom editor [1] bundled with atom plugins, such as OmniSharp [2]. And while Atom is impressive, that's not Microsoft's doing, plus they took an open-source project and released something which isn't open-source and named that in a way to make people believe that Visual Studio is now all of a sudden cross-platform. Well, I think I'll pass for now.
Rebranding or not, doesn't matter (A lot of mainstream projects out there start like that). The point is that they are pushing to be a company that supports a cross platform development, so I'm surprised that you'd even bring that point. Also, CoreCLR and .Net are their own, and no, unlike what you think, they aren't going anywhere so soon.
And forget about Linux - if extensions are going to get distributed through the Windows Store, as this article claims, you can say goodbye to OS X support as well.