Microsoft launched their Expression Studio 4 today (7 June 2010), as expected. It includes Sketch Flow, Expression Encoder, Expression Web and Expression Design. This release comes with the Upgrade version. If you already have the licensed copy of Expression Studio 3, it will auto update to Expression 4 and you need no new license.
You can download it from Microsoft Expression Studio site.
Please note that, if you are developing in Silverlight for Windows Phone 7 and want to use Expression Blend, don’t install this version of Expression Studio. Continue working with the Expression Blend 4 Beta and the Windows Phone 7 CTP Tools for developers. Once the Windows Phone SDK releases, there will be service pack for Expression Studio.