From June 30, 2009, PMP Exam will be based on PMBOK Fourth Edition. I did a quick survey of new PMP Exam Prep material based on the new PMBOK Guide. As expected, very few publishers have managed to release the upgraded versions of their Exam Prep books and other resources. Many have announced the plans and the books are available for pre-order on Amazon. Surprisingly, there's no word on the upgraded version of the mother of all PMP Exam Prep books - PMP Exam Prep by Rita Mulcahy.
Update Dec 3, 2013: Links have been updated for PMBOK Guide, Fifth Edition
Here's a list of new books for the PMP Exam:
PMP Exam Prep Books for PMBOK Guide 5th Ed