Even if we could trade for Sabonis, he doesn't fit what we want most. He's not an elite defender, not a rim protector.
Turner is the shot blocker we all wish we had, but IMO, no way Ainge should or will pay the price. Turner is good but not great offensively, other than a nice 3 pt shot he's developing. But he isn't a commensurate talent compared to our big 4, and we can talk about it all day, Danny Ainge will never, ever trade Marcus Smart. Smart is the Celtics, the heart of the team, and I think Ainge looks at him as the heart of not just the roster, but the entire organization.
I just can't see anyone out there available who might be worth the price. KAT obviously, but the price for him will be almost as steep as AD, and probably totally unavailable anytime soon.