I think terry is gone for a few reasons:
1. His age is starting to show as he appears to have more and more difficulty creating offense for himself.
2. His overall performance thus far has been sub par
3. There's a glut at SG and someone is going to have to go as trade bait for a big.
4. With the defensive play of Lee and Bradley being so dominant and both coming around to being able to hit that three pointer, Terry becomes expendable.
5. It comes down to Rondo or Terry being traded this off season. Rondo isn't going anywhere and Terry would have the same problem fitting in and getting consistent minutes next year.
I think the Celtics will move forward with the younger backcourt of Rondo/Bradley/Lee/Crawford and terry will be gone. He was brought in to be the scoring piece off the bench that(along with Jeff Green) solved those long scoreless droughts the bench would go through. It didn't work out that way and then the injuries started.
With the contracts Danny signed late in the year(Williams, Randolph, White) being extended into next year, I see Terry and a couple or all three of those guys being packaged for a player, sort of the way he has done so in the past. Williams, White and Randolph were signed for the future as trade fodder and filler and I have to believe that those three contracts and Terry's could bring in a $9-10 million a year big man.