A lot of very thoughtful, well-written replies on both sides of the coin.
As the original poster of this thread, one thing I'm not going to debate as all is Larry Johnson's outlook for 2007. He is the consensus #2 RB and barring an injury, I feel he will finish as the #2 RB... if not #1. I don't think Johnson will wear down from this season alone, and I think he'll have a very good 2007 season.
What I really want to know is what you would do with him if your team just really stinks. Obviously, if you're a title contender, you hold LJ and ride him as far as he'll take you. On the other hand, let's say you have Johnson and really not much else - a bunch of rookies and upside guys along the lines of Brandon Marshall, Marcedes Lewis, etc. Next year is probably not going to be the year unless a lot of players get a lot better, and fast.
In this situation, do you hold LJ and hope the rest of the pieces begin to develop? Hold him and hope he's still the same LJ in 2-3 years? Or do you send him packing now for a package?
In the end, I guess the answer lies in what "the package" is. If you can get multiple picks and a solid RB/WR, it might be the right play to consider it - even if you think LJ will continue to be the same beast he was in 2006.