I'm in the run-around now. I purchased AP's on 9/15, to activate in mid-January. I emailed through the website asking if there was anyway to get the 13th month promotion applied to my vouchers, was told to call the ticketing services center (407-566-4985, option 5). I spoke to a woman there this morning who told me purchase date doesn't matter (even though the website to purchase AP's explicitly say "And if you purchase an annual pass now through January 3, 2017, you get 13 months for the price of 12!"). She told me all they have been told is that it is based on activation date. I asked for a refund so that I could repurchase under the promotion, and she was unable to refund me because I used my Disney Vacation Account and she wasn't able to issue a refund to that. She gave me another email address to contact and ask them if they can apply the promotion, or refund me.
So, I guess we'll see.