Just want to mention that it's not a question of "owing" the Pens anything, it's about what he wants to do in the twilight of his career. And it's perfectly reasonable that he's more interested in giving back/helping the young guys then he is in chasing personal glory by going for another cup.
Now sure maybe he'd "help" more by being traded, but that's somewhat debateable. I mean a big reason a lot of us want him is so that he could have a lasting influence on our own young guys as they learn from him. In fact him helping by being traded is entirely dependent on how good the Pens scouting is, because drafting busts doesn't help. And drafting a bust is entirely likely given that the picks he would garner would be late 1st which are notoriously bust prone, and the Pens have been terrible at drafting for some time now.