I seriously dislike these "doctor" threads. Here are a couple of obligatory statements that go in all of them:
"Every body is different, healing is a process"
"The last thing you want to do is jeopardize a career for a few games"
Oh and one that applies specifically to this thread:
"You don't know anything about this because you haven't ever seen Rondo's x-rays and all you know is what the media reports."
I find that one to be spot on for all of the medical speculation including the OP.
Here is some basketball speculation. Rondo's timeline changed dramatically when Ainge changed his entire team in the span of two weeks. I imagine that Rondo could have been back by training camp but probably not 100%. He's probably the toughest PG in the NBA so I won't question his will power. However, even with a championship contending team I wouldn't have wanted him back until December or January.
Now Ainge is moving pieces and parts, probably trying to get bad for the lauded 2014 draft class and Rondo (should) might have different priorities. I imagine he felt some sense of obligation to PP and even more so to KG to get back as fast as possible and contend. Unless he's traded I doubt he's coming back until at least January, regardless of his medical clearance. Honest to god if he's a Celtic come the start of the season I don't expect him to start playing games about 2-3 weeks before the trade deadline. Just long enough so that other teams can see he's still a great PG post surgery.
The end of my speculation is that Rondo will be traded either before the season starts or at the deadline. I don't think he's a rebuild guy and I don't think Ainge is willing to risk landing out of the lottery by letting him come back early. Any fool can see that Rondo/AB/Green/Sully/KO is better than at least 10 teams in the NBA. I'm sure Ainge sees it too.