The Hawks are being slept on, in my opinion. Horford and Millsap is a nice frontcourt, and hopefully Sweet Lou comes back healthy. He and Teague make for a fun-to-watch backcourt. Korver slots in nicely at SF. The Hawks will have the floor spread next year. I expect them to be above-average offensively.
The Bucks are depressing, really. A rotation of:
Knight/Udrih
Mayo/Neal
Delfino/Giannis Adegreekrookie
Ilyasova/Henson
Sanders/Udoh
is good enough to make to the playoffs in the East. Despite losing their starting backcourt, I see them playing very similarly. Personally, I like Larry Drew as a coach, so I think he'll do a good job there. They'll fight for the eighth seed.
The Raptors looked good post-Rudy Gay trade last year, and I expect them to build on that now that Bargnani is gone. Lowry is a solid starting PG, and they have an uber-athletic wing rotation of Gay/DeRozan/Ross. Amir Johnson and Valenciunas up front is nice, too. They'll be in contention for the postseason.
The Wizards and Cavs could miss the playoffs if health becomes an issue. Both Wall and Irving are very talented players, but they've struggled to stay on the court. If those two can play through the whole season (a tall task, but I think they can do it), Washington and Cleveland are both going to compete next year for a playoff spot.
That leaves the Celtics. A lineup of (this is what I think is our best rotation):
Rondo/Crawford/Pressey
Bradley/Lee/Brooks/Bogans
Green/Wallace
Sullinger/Bass
Olynyk/Humphries/Faverani/Melo
could contend for the playoffs. I think it depends on how long Rondo is out. Reports are he'll be ready for training camp, so that's good news. I think Danny is going to make lots of moves at the deadline, so I don't see the roster looking like this in five or six months time.
My final prediction is that the Hawks, Wizards, and Cavs make it, with the Raptors, Celtics, and Bucks missing out.