You're right about the PMBOK version 5. It was released the beginning of the month (in fact, it was released on January 1st, 2013).
According to PMI, the new PMBOK will be used for the PMP as of August 1st, 2013 (which is a Thursday). This means that the last day for you to take the exam is July 31st, 2013 (this is the last day where the PMBOK version 4 will be used for the PMP).
In any case, the difference between PMBOK version 5 and PMBOK version 4 is not substantial as the difference between PMBOK version 4 and PMBOK version 3.
Good luck on your PMP exam!