The new PMI standard for project management –PMBOK Guide Fifth Edition– (available from January 2013) will become active as from September, 1st 2013. Next update is scheduled for 2018.
Exams taken before July, 31st 2013 are still based on the old version (Fourth Edition).
More info on transition period here. Also have a look at the exam eligibility cirteria changes.
The PMP Exam Prep Book is now also updated and aligned with the PMBOK-5th edition.