Their really is no reason to trade him. First of all what would we get for him? Probably not much. I think that three things need to be done to maximize his use.
The first is that, like others have said before me, he needs early touches. And not just early in the game, but early in each quarter, or at least when he enters the game. The ball has to find its way to him.
The second thing is that Stevens needs to have more plays called for him while at the same time, he needs to start cutting to the basket more, playing a bit more off-the-ball. I think that when Rondo gets back though, a lot of that will work itself out.
Third thing that I have also read and agree with, is that we need a real first option. someone with the talent and the drive to dominate, and let Green be the quiet number 2 guy.
Number three is the tricky part though, but hopefully something will work out either through the draft or a trade by the start of next season.