Finally the WCF 4.0 certification exam is being published in less than a week. (July 2nd as Microsoft promissed). You can check the following link for more detailed information:

http://www.microsoft.com/learning/en/us/exam.aspx?ID=70-513&locale=en-us

Right now, there is no MS Press book to prepare for this exam but I truly like this book from Wrox. 

This MS course will be also availabe on late July if you can not wait for the book.  MCTs can use the course materials to prepare themselves for the exam. MCTs! Do not forget! There is a %65 off if you take this exam within 90 days of the publish date.

 Good luck! :)