If anything, we should be surprised that anyone's surprised. Whether or not TFA's theory is true, one thing is absolutely clear: .NET, like any Microsoft technology, has an expiration date.
Anyone remember COM, VBX, and other MS-Windows technologies of yesteryear? Or the Visual Basic debacle of more recent vintage. For as long as I can remember, there's been a steady churn of Microsoft technologies, coming and going.
Microsoft makes a lot of money from selling its development tools, documentation, etc... to its developer base. Microsoft simply runs the whole show. They are in full control, and call all the shots. And they understand perfectly well that if they keep the same technology platform in place, over time, they lose a good chunk of their revenue stream. That's why they have to obsolete their technology platforms, time and time again. They need revenue. It makes perfect sense. If you are a Microsoft Windows developer, one of your primary job functions is to generate revenue to Microsoft. Perhaps not from you, directly; maybe from your company. Whoever pays the bills for Visual Studio, MSDN, and all the other development tools. Maybe it's not you, personally, but it's going to be someone, that's for sure.
So, perhaps this is the death knell for .NET. Perhaps not. If not this time, maybe next year. But it's inevitable. It's a certainty. If you are a .NET developer, your skills will be obsolete. If you were a COM developer, or a VB6 developer, your skills became obsolete a long time. I see no reason why .NET developers will escape the same fate. It's only a matter of time, but that's ok: all you have to do is invest some time and money to retrain yourself on the replacement Microsoft Windows technology, whatever it's going to be, when its time comes. But, it'll come.
Originally I came from a Unix background. Many, many moons ago I explored the possibility of boning up on the MS-Windows ways of doing things. But, after a bit of some exploratory peeks and pokes, this became painfully clear to me; that whatever I learned, all of it was going go to waste, in its due time. And that was pretty much the end of my venture into the Windows landscape.
Well, I'm happy to report that read(2), write(2), and all the other syscalls that make up POSIX, and its derivatives, still work the same as they did decades ago. Everything I have learned, as the sands of time have rolled on and on, I still put to good use today, and I make a pretty good living using them. Nothing has gone to waste. Honestly, this is more than I could say for my peers who practice their craft on MS-Windows. A lot -- not everything but a lot -- they learned decades ago is now completely and totally worthless to them, and to anyone else.
So, whether Windows 8 is Longhorn reborn, as TFA says, or not, one thing can be said for certain. .NET is dead. It's just a matter of time. Good luck learning its eventual replacement. Of course, you understand that it'll be dead too, some years after that, of course; just keep that in mind, as you make your long term plans.