I don't really think there's too much risk of Microsoft taking C#/CLI (particularly non-classic Asp* stuff) behind the barn and killing it. It's both a bad move considering how many of the successful cornerstones of their business run on it or use it extensively (SharePoint, Reporting Services, BizTalk, OWA, Powershell etc), and would be breaking from a tradition of supporting existing versions of everything for far longer than is useful.
Silverlight could only be killed like it was because it's on the client. Classic ASP, a 15 year old technology, still runs easily on IIS 8 / Windows 8. Yes, Microsoft could kill CLI on the desktop and stop distributing .net frameworks (or by removing the desktop mode from Windows 9 and removing .NET support from metro etc), but it's almost as safe a bet as there is that you'll be able to use it on the server for at least the next decade.
Silverlight could only be killed like it was because it's on the client. Classic ASP, a 15 year old technology, still runs easily on IIS 8 / Windows 8. Yes, Microsoft could kill CLI on the desktop and stop distributing .net frameworks (or by removing the desktop mode from Windows 9 and removing .NET support from metro etc), but it's almost as safe a bet as there is that you'll be able to use it on the server for at least the next decade.