No, we are still there and alive!
However if you go through the left hand navigation of SDN you will notice that will not find link to the .NET Interoperability area any more.
The reason is that the left side navigation has been restructured according to the new SAP technology map.
Still the .NET interop page available using the link http://www.sdn.sap.com/irj/sdn/dotnet and the documents can be accessed through search.
The .NET inerop page is now linked as a prominent link on the entry page to the SAP NetWeaver Capabilities.
In the left hand navigation just click SAP NetWeaver Capabilities.
This screen shot shows the link on the SAP NetWeaver Capabilities page.