Microsoft listened to our requests. It has announced its upcoming tool for generating MSDN-like documentation from your .NET code. The codename is Sandcastle and the tool is presented as a "Documentation Compiler". It should work the same way NDoc does, except it will support .NET 2.
The first release has been delayed and is now planned for August, as part of the next CTP release of the Visual Studio SDK.
The information comes from Microsoft's forums.
Update: an alpha version is now available.