Great news from Scott Guthrie:
When we originally announced Expression, one of the common questions/complaints was over why we weren't planning on including the products (especially Expression Web and Expression Blend) within MSDN subscriptions. Today we announced that we were changing this (you can read details on Soma's blog post announcing it here).
Expression Web and Expression Blend will now be available at no extra charge to all MSDN Premium Subscribers (this includes customers with the "VS Professional with MSDN Premium" subscription). This means many more developers will have awesome design tools for building great ASP.NET, WPF and "WPF/E" solutions.
No such luck on Expression Media and Expression Design, though. At least not yet.