Yeah, if they keep Rondo and Green, they should be competing for the playoffs in the east. Of course it remains to be seen if those guys are still here in November.
So...whats the difference between having rondo and green last year and not making the playoffs, to this year making the playoffs??
I think there are likely to be a few more differences than just those two.
A balanced roster (featuring an at least _adequate_ true center and a true starting point guard for the whole season, not just every other game the last few months) is in itself a major upgrade.
Shocking idea: NBA players tend to play better after they've had more than a year or so of experience. It's not an unreasonable expectation that Sully, Olynyk, Bradley, etc., will be better players this year than they were last year.
Further shocking idea: Players tend to execute a coach's system better if they've played in it longer together.
Finally: Rondo & Green will both be in a contract year.