I would dearly love for the C# type system to get a bit stronger and less verbose. It's also confused, I think, because you have explicit classes, anonymous types, and dynamic, and they aren't always very well put together. I actually also like what Anders did in TypeScript around structural types, and wouldn't mind some of that mojo in C#.

I take your point about pace, though. I wonder how it compares over the same timeframe vs other languages? In the 5 years for C# to cover that distance, what have other languages achieved? The biggies are particularly interesting (JavaScript, Python, Ruby, Java, C++, etc) because users probably demand more in terms of support and compatibility. (For others contributing, I'm thinking language-specific, so not libraries, frameworks, or runtimes, just pure syntax.)

It's also worth throwing uptake into the mix here; it's not much use if there's a version of the language defined in a spec but everyone's using the compiler from 1999 (JavaScript, I'm looking at you) I'm not a pythonista but I understand Python 3 has struggled with uptake, too. Not too sure of the details; happy to be corrected.