I've had every iPhone since the 2nd one and AT&T waived the upgrade fee every time except for last year, when I was required to pay the early upgrade fee of $250 + cost of the iPhone 5. It took me three times of calling customer service, asking nicely and citing other examples of credits/waivers until I finally got someone that was willing to help. She was very nice and gave me a bill credit of $250 to offset the $250 I'd paid to upgrade but told me not to expect this to happen again. She said she would note the account and specify that a one-time courtesy credit was applied and that the customer understood that such courtesy would not be extended again for an early upgrade.
I think it would be a waste of my time to ask again this year, but everyone's luck is different I suppose.