A team, I dont know how big it is, has worked very hard on the 4th Edition on the PMBOK (Project Management Book of Knowledge. Pat Weaver covered in his blog the key aspects already. It does not seem to be the big leap, how ever, several usefull clean ups have been incorporated.
So know its time to order it as part of the Christmas rush and with a discount if you order online via PMI. So buy yourself a Christmas present. But rush, promotion ends by end of this year.