Here is the section for the specific updates for XNA, new improvements in .NET 3.5 and what is coming up for .NET 4.0. This refreshes the previous post from Digipen for more up to date info.
1. C# 3.5
With the release of Visual Studio 2008, the C# language has been updated to make use of .NET 3.5.
If you follow this link, you will see what was added to .NET 3.5 which is what XNA is based upon and follow this link for what... read more