Missed the session about C# 6/.Net 5 at Build? (Well there wasn't one, BUT Anders DID talk it up in this C9 Live Interview)
Anders Hejlsberg and Charles Torre talked about a future version of C#, version 6.0, at Windows Build 2013. http://channel9.msdn.com/Events/Build/2013/9-006 (34:30)
Visual Studio 2013 is the minor release version in an annual major/minor release cycle. The version of .NET included in VS 2013 is 4.5.1 which is an in-place upgrade of version 4.5. Major changes are expected for Visual Studio 2014 and .NET 5.0.
C# 6.0 will feature an all new C#-based compiler based on Roslyn, which will be released with VS 2014. Roslyn is currently available as a community technology preview, which opens up new compiler services for third parties. The C# team aims to make Roslyn as close to the performance of the native compiler as possible (within a factor of 2 during development and better on release), and, in some cases, Roslyn already outperforms the native compiler due to a more modern immutable AST architecture that supports parallel compilation. The immutable AST architecture is detailed in a recently filed patent.
The transcription of the pertinent section by Wesner Moise is awesome. While I felt it s shame we didn't hear about much of the future future stuff (C#6, .Net 5, Roslyn, etc) this interview gives me hope that there at least will be such a release (not that I didn't think there wasn't [Is my boolean logic right?], but still it's good to hear it from none other than Anders himself...)