Ainge may have tried to tank this season by refusing to get a replacement big, so we'll see. Perhaps he was hoping to get a #1 the way the Bulls were able to draft Derrick Rose without completely emptying the roster of talent. I'm not a fan of starting out a season in tank mode, but it is something to consider if the team is foundering in mid-season.
For now, I think the team is basically committed to one more year if KG and PP do not retire. I do feel like the team has a shot if they can dump salary (a guard, not Bass) to sign a big. My pipe dream is a salary dump of Terry and Elton Brand being available for the MLE.
Otherwise, I think the team should wait until Rondo is healthy and playing 30-35 minutes per game or shows that he can't handle that anymore.
The time to really consider blowing things up in Boston is when the medium contract role players such as Bass, Terry, and Lee become expiring contracts. Which is after next season. That can start a few months early if the Celtics play poorly enough that a mid-season shift to tanking is a good idea.
This all goes out the window if Ainge finds a deal which can pair a potential All-Star with Rondo.