Thanks to Steve Hall for pointing out the location of the following information.
You can get the current status of all language features that will be present in the upcoming C# 6.0 release, as part of the Roslyn compiler platform project. Here’s the link to the page on Codeplex containing a current list of features:
For reference, below is the list of planned C# 6.0 language features, as of 24 Oct, 2014.
Features that are “done” (already implemented):
Features that are “planned” (intended for the release):