Stop these threads.
First off, why do we want to trade our best players? Do you actually wanna be worse than we already are?
Second, he will not (repeat: WILL NOT) fetch you much value in a trade. Most teams in the NBA already have their franchise point guard, and don't need Isaiah. He's not gonna get you much in a trade. This leads me to my second point. If no one will give up much for him, what makes you think he will successfully receive a max contract after his current contract is up? Those same teams that won't trade for him are not gonna sign him either, especially at the amount that he wants. Why then, should we worry about him pouting and wanting a max contract? No other team will give him one, for the same reasons that we're scared of giving him one.
Therefore, I think it's very obvious that Isaiah will sign a team friendly deal in the summer of 2018 to stay with the Celtics, who have essentially been his home and the only team that actually took him seriously and let him do what he wanted. That stuff matters to Isaiah too. He's not just chasing the money (even though we heard the Brinks trucks comment and all).
To conclude, he won't get you good return in a trade, since teams are wary of his height and because teams already have their franchise point guards already. Therefore, it's unlikely that they'll give him a max contract either, for those same reasons. As such, it makes sense that he will return to the Celtics on a moderately priced deal. Case closed.