The chances are no different than they were this last year. There is nothing tangible to say otherwise. Odds on a line are one thing, real world results are reliant on a few factors that fall in favor with the Hawks. Age and stability of roster, injuries, style of play and repeated success with that style of play.
A 3rd appearance is not unreasonable just because some other teams couldn't do it. They weren't supposed to make the playoffs, win a playoff game, make it back to the Super Bowl either. They came up 1 yard short without their interior DLine intact, starting TE, starting FB and one very important slot corner, and edge rusher, both of whom were needed in the SB big time. I like their chances.
I guarantee that there are at least 20 teams that feel they have a good chance next year with less on their resume.