I've heard rumors that the new book would come out either around christmas or around PoA movie premier.
I don't think either of those are right... although if it was around christmas that would be a lovely present!
Those names are all quite good and I can't pick just one, but some sound like chapter titles... ^^

I've also read that she would not continue anything about Harry Potter after these books were done. J.K. said she wanted to write a romance novel, but with all the publicity with Harry Potter she most likely will have the same problem as A.A. Milne.