I don't think they were every going to really "run it back."
To my eyes, the extended contracts for KG, Pierce, Doc and Terry seem to have been written with the idea for a bit of a farewell tour as the team readjusted toward working around Rondo with players who, on paper, would thrive with him at the point--guys like Bass, Lee, Green, and Bradley.
Doc is there to provide confidence in Rondo and continuity for the new pieces, and leaves the team in solid shape for a post Big 3 era.
Unfortunately, Rondo had his ACL injury, and the team was put in a position of relying more heavily on their aging stars (and clearly best players) than they would've liked. Since we're probably looking at the first half of the season with Rondo rehabbing (I don't expect him to be back to form until January), the prospect of carrying half of a season on the aging legs of Pierce and KG probably didn't appeal to either of them, Doc, or Danny.