From the features they are porting into the language I think this is the case; albeit C# will always be the more verbose language and the features will feel somewhat clunky at times IMO. Pattern matching, async yield return, async/await, etc all were in F# in some form beforehand with features like records and DU's probably being investigated as well. When I read a new C# language version announcement it does feel like I'm reading a subset of the F# feature list.