You know, as I think about this from a fan perspective, rather than a Castonzo perspective, I try to play the"window of opportunity" game.
When one looks at the assembled players in the last 2 or 3 years and juxtapose that with the team build and future growth, Anthony sits a little outside that window. I love him as a player, and I think he has been vastly underappreciated by fans. I even see some who practically called him trash, now wringing their hands at his possible departure.
I think most of the players at his age see this as a body/earnings business decision far more than fans are willing to recognize. We can discuss the window of opportunity angle till the cows come home, and as seen here, the conjecture will abound. In the end, for the player, it is far more likely that his decision is about whether he wants to put more degradation on his body, regardless of who the QB is or the immediate future possibility of a SB.