After this year I think he'll go to an American League team so he can be a DH. But I don't see him going back to Boston. They didn't leave on the best of terms.
He will not be back in Boston this year, next year, or any other. That ship has sailed, and there's no interest from either side in bringing him back to Boston.
B) I don't think the team or the fans would ever want him back, besides, he's old, not as productive as he was when he was using "fertility drugs", and will probably retire after this season or next season.