We had ITIL V3 in 2007 (and 2008 and 2009 if you are talking exam syllabus), and PRINCE2:2009 (why not PRINCE3? - it was a sweeping rewrite). Apparently we have also just had PMBOK 4th Edition.
In both cases of ITIL V3 and PRINCE2:2009, OGC/APMG have cavalierly assured users there was little difference and they should happily continue to pay for the old exams up until the time it is no longer convenient for the training companies for users to pay for the old exams. And of course in both cases this was crap, with the new syllabus being totally different.
The new PMP exams are due June 30th. How different will they be?