Expansion drops 11/13/14. That's 2.5 months away. They drop pre patch roughly a month before expansion release. Pre patch has to be tested, and will be available on the PTR. That means it has to come out soon in order to be tested on the PTR before it goes live.
I give it one or two weeks. Three at the latest.
Pre patch will also have most of the changes that impact low level players: tuning, ability shuffle, talents, ect.