Unless you get a response from someone that works DIRECTLY with the firmware testing, all AT&T frontline support will do is give you speculation. Their job is to get you off the phone as quickly as possible with a satisfactory answer.
In all honestly, it's ULTRA rare for anyone to get an exact, correct answer from AT&T for a firmware release. I have only seen it once, and it was because someone started arbitration with AT&T (for the Lumia 830, AT&T sat on it's firmware for 5 months based on it's build date)
While AT&T will still put Windows Mobile up for sale, support is a joke.