I don't think the Celtics can win a title next year for a few reasons:
1. Pierce is cooked
2. KG needs a year of rest
3. Rondo, even he comes back well, will not be able to push like usual in next year's playoffs. Rondo also needs a year of rest as he has a TON of mileage.
I think the coming season needs to be a season of bringing back Rond very slowly, playing the young guys a lot, playing KG 18 minutes a game. Pierce should be released or traded to play one year elsewhere. If he enjoys his new home can stay there. Otherwise he can come back the following year to play off the bench for the Celtics. The team will end up in the lottery in a great draft (2014), and probably get something like the 8th pick.
Then, to begin the 2014 season, the Celtics will have a rested KG entering his final year, a rejuvenated and rested Rajon Rondo, a seasoned Jeff Green, a healthy and heady young Jared Sullinger, Pierce off the bench for his final year of bball, an acquired stud backup PG if Twill doesn't pan out, a couple of sharpshooting wings, and most importantly, 2 new centers who can rebound and protect the paint (coming through draft or free agency or a combo).
Its a chill out and tank plan with a run it back feature tacked on....
(low minutes for 2 of the run it backers...but that's okay because Pierce and KG, especially KG, add the structure a team needs to win).