If you are someone who doesn't think IT can be a part of what Ainge is trying to build, then this trade makes sense. It's not bad for every team involved, if Philly still places much value on Dunn.
Having said that, it will never happen. I don't think Ainge will trade IT. With his huge #s this year and fans loving him, he's like a little monster that grew out of Ainge's control.
Whether you think he's a piece of a championship puzzle or not, I think we're going to keep and re-sign IT and he'll be a Celtic for at least another 3 or 4 years.