Update #2:

I don't know why but technical community tends to see things in very absolute black/white terms when the reality is full of shades of gray. This is a response to several new comments that were added to this post:

1. .NET framework will not go away any time soon (or ever). Just about every technology that windows had since 90's is still around in some form or fashion. So for those that are so attached to .NET framework: a) don't worry about it disappearing and b) stop arguing in its favor as if your life depended on it, your API is safe.

2. WinRT does reimplement a lot of functionality that in the past was provided by Win32 and .NET framework APIs. People who want that functionality will have a choice if they want to use WinRT, .NET framework, or continue with Win32 API (that's not dead either). If WinRT doesn't support easy creation of web applications today, there's a very good chance it will support them in the future.

The position that Microsoft announced is that WinRT is a large framework which gave Microsoft a chance to start with a clean slate and built an API using lessons learned in Win32 API and .NET framework itself. I did try looking for that video, and still can't find it, but one of the things the speaker mentioned is that there are certain areas of .NET framework which could have been defined better/simpler/cleaner and WinRT exposes that same functionality in that new cleaner interface.

UPDATE #1:

Since I just got a 'nice answer' badge for this, I thought maybe I should come back and a) clarify few things and b) make the fact-checking police happy because as we all know on technology forums anything inaccurate could result in wars that last for years.

1. WinRT is not a replacement for .NET framework, but it is yet another alternative that MS Windows developers now have and MS is strongly pushing people to go in that direction. It appears (please hold your flames if this is not 100% accurate) that WinRT was primarily targeted for Modern UI apps although regular desktop apps should be able to take advantage of it as well. Having said this, MS is strongly pushing for people to switch to writing a) modern UI apps and b) start using WinRT so as the balance shifts percentage of people using .NET framework will most likely go down.

2. C++ will NEVER replace higher level languages such as C# or python. Just like those languages will NEVER replace C++. This was probably the most controversial part of OP's question. But it is all about the balance and the facts are that:

• C++ community (with MS being large part of it) is pushing for a strong comeback to position C++ as a good language for low-powered devices, whose market share has been going up like crazy lately. If you do not believe me, search for "GoingNative" series of talks that began last year.
• With all the effort and influence from Microsoft, C++ usage will definitely go up, while C# might drop some what. This is what MS is pushing for and as I said in the comments above, when MS puts their capital behind an idea, they do shift large portion of the industry. I will probably get a response from some guy who will argue, "what industry, I've always been on Linux" and to that my only response is, wake up! Yes, there are other OSs out there but majority of desktop market, both consumer and business at the moment is Windows and any serious developer who wishes to maximize the value of his time would be very silly not to target that chunk of the desktop market.

So in conclusion: Yes, MS is pushing for C++ to come back so most likely its popularity will increase. No, C++ will never replace C#.