State machine functionality in WF 4 will be a part of the upcoming Multi-Targeting Pack for Microsoft .NET Framework 4 Platform Update 1 (KB2495638). To create State machine workflow applications in Visual Studio 2010, the MT Pack for .NET Framework 4 Platform Update 1 will be required. This update will be downloadable soon at under this link.
More information about this you can find here.
Apr 11 2011, 10:47 PM