Actually Carbonneau said a few times this season the he asks his 4th liners to be more than just playing well defensively (which Chipchura could to better). They have to score goals, bring intensity, be efficient on the power play, win faceoffs, etc. And Chipchura is not doing it. He's not a total liability, but playing like Andreas Dackell and Niklas Sundstrum isn't good enough to earn a spot on the team over other guys.
I'm absolutelty not a Chipchura or any other player basher, but if you want to play in the NHL you have to bring something to the table. And he's not.
If I'm not mistaken he'll have to clear waivers to be sent down next year. So he has until then to prove that he's more than an mediocre 4th line player, or else he will end up in Atlanta/Long Island.