Unless Boston could do a sign and trade for Noel or J. Green, I honestly think I'd take a flyer on Bosh. No one else moves the needle at all so missing out on them does nothing and is thus worth the risk.
If Bosh is able to play 10 games, his salary goes back on the Heat's books, pushing them far into the luxury tax this season and next season. Might see them forced to make some salary dumps.
In other words, even if it didn't work out, there is still value in Bosh. But I think he's done, and finally accepted it. And I can't anticipate the Celtics being a team to try to convince him otherwise.