Now please, don't bash me for saying that, but it's an interesting thought.
Obviously both teams have vastly different rosters/players (besides Horford), and Atlanta won 60 games that season while Boston are expected to win around 51-53 this season. The Cavaliers were still trying to improve their chemistry on the court with a relatively new team intact, so they finished 2nd back in the 2014-2015 season.
Similarly though for BOS and ATL, the expectations were that Atlanta would be a middle of the pack team that year, but they surprised everyone and finished #1 in the East, and were on fire for much of the season. In Boston's case now, people expected them to be the #3 or #4 seed, but no one (not even us probably) expected them to have a solid hold for the #2 seed, and a legit shot at the #1 seed (esp. with Love injured now).
Lots of people brought into the hype that was Atlanta, but another good chunk of people thought that Atlanta were just overrated.
That Atlanta team did win two playoff series, but got humbled by Cleveland and "Playoff Lebron" in the playoffs. People thought ATL could beat them, but were surprised that they were completely outplayed by the Cavaliers in the playoffs, and got SWEPT (not even one win).
Now here are the Celtics, a team that could get the #1 seed, but I think it's fair to say that if BOS meet CLE in the playoffs, they will lose to CLE in a 7 game playoff series. They would battle and have hard fought games, but I think the Cavaliers ultimately win the series especially if Love returns healthy late in the season for their playoff run.
But as KG said, "Anything is possible", and I hope the Celtics can have a cinderella run in the playoffs and make a lot of noise.
Let's hope they have the same luck in the ATL 2014-2015 campaign in the sense that they make the ECF, but hope they can take Cleveland to the brink in a hard fought playoff series. I'd LOVE to see that.