I understand the sentiment, but don't agree with it. Give it out to whoever needs a jersey. He's not worried about us, he retired and became an Oakland Raider. And good for him.
He got paid a lot of money to play here, and they let him leave with a lot of money when they could have asked for it back. They also facilitated his move to Oakland Raiders. So I don't think we owe him anything.
I love what he did for this team, but Marshawn was for Marshawn. Pete and John rescued him from Buffalo and put him on the road to a Superbowl and possible HOF. Pete also let him get away with things that no other player got away with. Again, I don't think we owe him anything.
I'm a bit sentimental about the number, and what he did here, BeastQuake, wearing down defenses, but would he have gotten those opportunities anywhere else?