What if they can't add enough to TD, TP, and Manu to be serious contenders? Expecting a series of transactions that transforms our ineffective, loudly condemned, bench into a championship supporting cast is very optimistic.
Do you spend the next three years fighting for a playoff spot and exiting in the first round and then rebuild after Tony has left in 2011 and Tim retires in 2012?
IMO, if the Spurs conclude that they cannot add enough to the Big 3 to challenge the Lakers, Cavs, and Celtics (not to mention the Rockets, Nuggets, Magic, and Blazers) they will have to consider trading their best assets. That means Tony or Manu.
The point of my post was that trading Tony for another elite player is an unlikely event. The only trade I would consider for Tony is one that brings upgrades at several positions in return. In the Portland example, the Spurs could get a package that includes several of the players from this group: Frye, Outlaw, Webster, Fernandez, Batum, Rodriquez, Blake, Bayless. Three or four young players, draft picks, and cap flexibility could be attractive.