Sixers don't have to trade Iverson. They're just tired of him and he wants to go so they're letting him go. They just really fucked up by going public about how desperate they are to dish him off. Had they been a little more subtle they probably could have gotten more value for him, but now teams know they're desperate to offload him so they're just buying time waiting while philly get's less and less picky about compensation. He's the reigning scoring champ, makes 20 million a year and he's not playing. Brilliant.
That's why so many nba teams (knicks??) are so screwed, these contracts are all guaranteed money. So you get all your dollars wrapped up in one or two guys and one get's hurt, one's a bust, and your stuck up against the cap for the next 5 or 6 years. And nobody wants to take the guys off your hands at the $$ your're paying them.
Iverson will get his money of course, but he'll wind up someplace terrible, the sixers won't get fair value in return and basically everyone loses in the end, except the owner of whatever shitty team he goes to...at least he'll sell a bunch of tickets for the next two years or so, until fans realize that even with iverson on the team they're still losers.