While that's one way of looking at it (and you could be right about this specific situation), the other side of the coin would be his limitations in talent, his inconsistent play in the 4 overall years, and the whispers about his attitude and maturity issues.
Just looking at his off-field issues since he came here:
--sex tape
--chat roulette on the constant, reportedly showed his penis
--tweet regarding "cocaine and Jack Daniels" left for Santa Claus
--other odd twitter messages that the media implied could be hints to his displeasure with Belichick and the team in general
--decision to skip offseason workouts
--instead of choosing to shovel his driveway like the rest of the players, he decided it'd be much better to post snapchat pics of his Porsche and the snow.....twice in a 20 min span....during the week of the divisional playoff game when other players made the necessary arrangements to make sure they were at work
I'm not claiming that any of these things are the reason for his possible departure or that they are severe enough to warrant him leaving, but I am noting that there have been hints about his immaturity and attitude concerns to take into account before we go blaming Belichick.
There is also the fact that there were a nice group here who were starting to call him a bust about halfway through the 2011 season, when he had looked lost in his first 1.5 seasons here. He turned that around down the stretch run of the 2011 season, and that led to a great 2012 season. The problem of inconsistent play seem to come up again in 2013 however, although some of that can probably be attributed to the injuries on the defense just as well.
In the end, I actually hope they keep him, but if they do it would be on their terms for a cheaper hope in price, and the cards are looking like he's probably going to be a player on another team at this point. Good luck to him.