Just a few thoughts:
1) If we are going to trade Mike or Brad, it is more likely that either will be traded ALONE given the length and size of their contracts. If we are going to trade Peja, it is more likely that he will be packaged with Corliss, Skinner, or any of our role players given that Peja has an expiring contract that is undervalued. I guess if we want to get rid of some role players with big contracts, Peja may be the bait. If we trade Peja straight up, we will not get a player of equal value in return, especially since big man are worth more in the NBA. If we want to get equal talent value for Peja, it will probably have to come as a sign-and-trade next year when the monetary value of his contract goes up.
2) Although no one is untouchable, I doubt we will trade Mike because he is the floor general that makes the offense run. If we want a big man in return, we BETTER also get a PG in return because I can't see Jason Hart running our offense as our starting PG. If that is the case, I doubt we can get a quality big man in return if we have to also get a PG in return to replace Mike. This is not the season to lose both Mike and Bobby at the same time...you will lose all blueprint of all that has made us successful at the PG position.
3) I also doubt we will trade Brad because he is the only guy in the high post who can run the pick and roll offense. With our recent acquisitions of athletic guards such as Wells, Garcia, Martin (from last year), the success of these guards will be predicated on a big man who can set picks and pass the ball to them. That man is Brad. Since we're already lacking in size in the front court, trading away an All-Star center would only be reasonable if either Duncan or Garnett was in the picture (and the Spurs or Wolves would be crazy to trade their cornerstone of their franchises).
My best guess is that we won't trade any of our core (Mike or Brad for position reasons and Peja for contract reasons) although we desperately need a power forward. Some way, some how, Petrie will get it done.