Welcome to Zombieland, the Metro Style Land of WinRT and the Undead

Silverlight is dead! WPF is dead! .NET is dead! Hey, they didn't talk about SharePoint or SQL Server at the BUILD conference, those must be dead too. Welcome our new Metro-id overlords!
We read such FUD everywhere these days. Actually none of these technologies are dead for the next several years! And you'll probably agree if you know the facts and not the FUD. So here are my thoughts based only on the facts I got from watching BUILD sessions, reading posts that stick to the facts and not listening to people who obviously didn't inform themselves, but nevertheless spread FUD around.

What happened
Microsoft announced the new version of Windows at the BUILD conference and the new Windows 8 runtime called WinRT, which is used to develop Metro style Apps. Metro style Apps are primarily focused on consumers, designed touch first and therefore perfect for modern multi-touch devices like tablets.
The good ol' desktop is still there and the usual Windows applications are now called Desktop Apps.
There's a lot confusion out there at the moment and many think only Metro style Apps are the future. Actually both models can exist side-by-side and I'm sure the mainly used UI will be the classic desktop for the usual business client. Metro is for tablets, maybe later for the phone. Desktop Apps will still work better for the classic business PC scenario in an office.
After trying Windows 8 I don't see myself using Metro style Apps a lot on my PC when I work at the desk. However, I will love to use it when I'm hanging out on my couch with a tablet. The good news is, both models are supported by Windows 8 and therefore can run on one device, including ARM hardware. Awesome!

WinRT

First and foremost, .NET plays a significant role in both development models and is not only used for Desktop Apps. I guess the FUD comes from the architectural picture above, where .NET and Silverlight are only represented by a small box in the lower right corner. Of course Microsoft wants to push the new Metro style Apps, the WinRT model and wants to get web developers into the boat, so they adjusted the graphic and marketing message accordingly.
WinRT is actually a new native COM library, plus some extra infrastructure. Therefore an app developer has not to deal with the COM stuff directly, instead you get a thin / fast projection layer (binding) for each of the supported programming languages. This projection layer is automatically built using WinMD metadata and provides projections for JavaScript, .NET (C# / VB) or C / C++. The UI can be designed with XAML or HTML / CSS in case of JavaScript.
The rendering is completely done using DirectX 11.1 (Direct2D) which results in great performance. In Windows 8 the rendering job is finally fully executed by the right processor. This architecture makes it also possible to implement the complete UI just with DirectX, which will usually be done by games. At the moment it's not possible in the Windows 8 Developer Preview to mix a XAML app with DirectX, which doesn't make much sense since the XAML rendering is done by DirectX. Fortunately all hints that it'll be possible in a later version of Windows 8, maybe in the beta.

The below picture by Doug Seven is a way more accurate picture of the Windows 8 platform architecture.

There are a few good, unbiased posts about WinRT out there, which stick to the facts:
WinRT: An Object Orientated Replacement for Win32
WinRT, the C++ Component Extensions
WinRT demystified 
A bad picture is worth a thousand long discussions.
WinRT reference with all namespaces at the unbiased MSDN, where JaveScript is just another language one can use for Metro style Apps.

WinRT and .NET
From what I have seen so far, coding Metro style Apps using C# / .NET seems pretty straightforward if you've done Silverlight, WPF or esp. Windows Phone development before. The BCL used by .NET WinRT is not the full Desktop version of .NET 4.5, it's a reduced set similar to the Silverlight types.
The design of the native WinRT COM library was heavily influenced by .NET. You see it everywhere. Type names, Properties, Events... Even WinMD is the .NET assembly metadata format.
WinRT types map to .NET types and copying of data structures at the boundaries is avoided by the projection layer to get the best performance. Only two types need to be converted using built-in extension methods. The System.IO.Stream can't be mapped to the WinRT stream, so there's an extension method. A Byte[] to WinRT IBuffer conversion is the other extension method.
You can even write your own, custom WinRT components in C# without decorating the classes with ugly COM attributes. Those components are then automatically exposed to the other languages using the generic WinMD metadata. So you can write a component in C++ or in C# and use it from a JavaScript WinRT project. Pretty cool concept if you ask me.
Many WinRT classes look like their origin is .NET / Silverlight and the WinRT WriteableBitmap is also very similar to Silverlight's implementation. So expect a WinRT version of my open source WriteableBitmapEx library in a few weeks when I'm done with the Mango updates for all my Windows Phone apps. After that I will probably port / rewrite some of my WP7 apps for WinRT.

The lifecycle of a WinRT app should  be quite familiar for a WP7 developer, since it's similar to the WP 7.5 Mango Fast App Switching. The lifecycle states are: Running > Suspended in RAM > Terminated. Apps get an event for suspending, not for terminate, so the state has to be saved during suspending. Of course an app should only be resurrected from the tombstone state if the app was launched, not when resumed. Apps get 5s for suspending and need to launch within 15s. Unfortunately we don't know the reference machine where those values are measured. Probably the low end configuration.
By the way, the Windows Store will be the better version of the WP7 Marketplace. It will include In-App offers, time limited trials and a very nice dashboard with a lot of analytic capabilities and insights.
In general should a WP7 developer feel most familiar with WinRT. Many concepts made it into WinRT and were improved and actually cleaned up.
My Silverlight MVP friend Morten Nielsen started a blog post series about how to port Silverlight / WPF apps to WinRT.
You should also read this post: WinRT and .NET and watch the ton of great BUILD sessions.

Conclusion

I welcome the new possibilities and great performance we get in Windows 8 with the WinRT. I'm sure Windows 8 will be an awesome tablet OS.
XAML has become a first class citizen and .NET is now installed with Windows 8. Microsoft is also working on a next version of .NET. Version 4.5 of .NET will bring better performance for WPF's ItemsControl for example. Seems not very dead to me. In fact, a Silverlight / WPF / WP7 developer's knowledge of XAML and the Silverlight runtime is more valuable than ever before with WinRT.
Silverlight 5 is still in development and wasn't even released. We don't know if it will be the last version or if Silverlight 6 will see the light of the day. For now I'm quite happy with all the features of Silverlight 5 and we can develop a ton of applications for our customers for the next several years.

One should also not forget how long it will take until Windows 8 is finally out and reached a critical mass. A lot of machines out there still run Windows XP. Windows 7 is way better and I guess the transition to Windows 8 will take even longer. Windows 8 will probably mainly pushed by non-PC multi-touch consumer devices in the near future.

This flowchart by the Telerik guys sums it up pretty nicely.

So get yourself informed and start coding away. Don't give FUD a chance!