September 21 - Babylon (Release)
October 25 - Mongolia
December 16 - Spain + Inca
March 3 - Polynesia
May 3 - Denmark
August 11 - Korea
If you look at that, it's been as late as three months before. I'd say wait until December to be sure (plus, December DLC is more logical in case people want to buy it as a Christmas gift).
Or one could come up this month and a double in December