Reagarding what Atlanta might be able to get in a trade of Smith, I'm of the opinion it's less than what most people think.
Atlanta is going to be forced to have to trade Smith soon, or risk losing him for nothing. Smith has made it known he wants out of Atlanta. Also, Smith hasn't exactly made any preference known as to where he would like to play. Teams will be reluctant to offer much in a trade for a one year rental they can't be sure will re-sign.
On the other hand, Smith is known to be good friends with our best player (Rondo), and has on more than one occasion had very good things to say about the Celtics franchise and it's fan base. I would have to think this would give the Celtics a certain level of comfort with making a deal for Smith other teams might not have.