From what I have read the Colts attempted to restructure Marvin's contract but Harrison refused. I don't know the details of what Harrison was offered, but usually a restructuring is an agreement to give the player the same amount of money, but over a longer period of time. If that is the case and Marvin said 'no', then that tells me he is going to want to be paid more than he is worth.
Aside from what I am speculating Harrison will expect to be paid, there is his production. I agree with Deus, from what I have seen he seems to have developed alligator arms. Last year he was thrown to 112 times, catching 63 passes. That's 56%, which seems rather low given the rapport between Manning and Harrison. Harrison had 656 yards and just 10.4 yards per catch, another number that ranks very low among NFL receivers. Regardless of his past, how much can anybody expect from a wide receiver that will be 37 before the season starts?
If he does play in 2009 I'd guess it will be for the Eagles. He can re-unite with McNabb, and be close enough to keep an eye on what's going on in his car wash and bar.