A few days ago Anders Hejlsberg delivered a presentation about the Future of C# at the Professional Developers Conveference 2008. He focused on the new things that will be available in C# 4.0:
- dynamic typed objects
- optional and named parameters
- improved COM interoperability
- co- and contra-variance
The recording of the presentation is available on Channel9 and worth watching.
A walk-through of these new features, together with several samples for dynamic typed objects, and simple variance, are also available at MSDN.
If you want to try them you can download the VS 2010 September CTP. Notice that it is available only as a VM image.