This week saw a major release from Microsoft: Visual Studio 2010 and .NET 4.0. There are not many feature changes from their Beta Releases. (Also see ScottGu's and Scott Hanselman's blogs).
As expected, there is nothing new in WinForms except the fact that it can make use of many new .NET 4.0 features like MEF. And of course, there will be bug fixes and performance improvements as the Group Manager of WinForms says in response to a comment in Somasegar's Blog: "We continue to invest in WinForms for .NET FX 4. This includes the core expectation of maintaining compatibility for applications already written in WinForms, fixing bugs that developers have reported, contributing to overall developer experiences across Visual Studio, as well as perf work and some feature development."
That "some feature" he mentioned is not to be seen any where. Look at the What's New in the .NET Framework 4 article in MSDN. It doesn't even mention WinForms!
Those who are still fond of WinForms find it comforting to say that "WPF is still growing and it need much attention unlike WinForms which is matured and used for many critical LOB applications around the world." :)