Not a lot of upside to trading Pierce for cap space. The amnesty card still looms if he significantly drops off as a player, and if not he's still a very good two-way player who can contribute a lot next year.
Unless it's for a younger fringe star (Granger, Gay, Horford, Josh Smith) signed longish-term or a high-level prospect (Evan Turner), I don't see the appeal.
I think Pierce stays on at least until the offseason, at which point he sees how we do in free agency. If we score some quality immediate contributors (my preferred scenario: AK-47, JR Smith and Omer Asik) and bring back Ray he stays on; if we take short-term gambles on inconsistent young guys (Beasley, A. Randolph, Javale McGee, OJ Mayo) and fill the rotation with Bradley, JJ and the two new first rounders, I could see him quietly requesting a trade.