If the Bucks want Pierce for Pierce (and they are not in salary cap hell), then they could be discussing a framework for a sign-and-trade for Monta Ellis or Brandon Jennings or even pieces like Samuel Dalembert, Mike Dunleavy, or JJ Redick. They could just be discussing who they would like to see the other team draft if they were going to consider including draft rights to those players in a trade.
Maybe they're even discussing Pierce, Sullinger, and draft picks for Larry Sanders and contracts if Sanders is insisting on a max extension and the team wants to sell high. Well, maybe not, but Ainge would probably try.