Most likely one of either Popovic or Pilar would make the team ahead of Valabik, Enstrom and/or Oystrick. Kwiatkowski is a depth move for the #7 spot and Chicago. Camp will determine who makes the team.
My guess is it went something like this. Chicago went looking for a veteran defenseman. As part of the lure, they promised they'd get him on an Atlanta contract. Since Atlanta, for once, isn't pushing the 50-contract limit, they said fine. This stuff happens all the time.
He plays in Chicago as the token veteran D and everyone is happy. Except the conspiracy theorists.
I'd assume he's gonna be in Chicago. Based on Enstrom's contract, it's safe to say that unless he really screws up in camp, he's got a very good shot at the Thrashers, and Popovic would have just about as good a chance.