I'd love to keep him, but I fear the financials will require them to use him as a sweetener when they trade Kemba or Thompson to clear salary.
I expect that they will be forced to explore that option given the basic facts
1. They can't afford to re-sign him, even to a team friendly deal, unless they move Kemba without taking back long term salary.
2. Smart on a one year deal has a lot of value for a team looking to make a deep playoff run right now; he has much less value for a team that is in the position of having to figure out a core rotation for the near-term. The Celts are closer to the latter than the former, in my opinion.