Fans in Dallas are really down on Carpenter. He's way down the depth chart, and it doesn't look like he's surfacing behind Ayodele, James and Burnett. The only reason they would refuse to dump him for a 5th is out of sheer embarassment, because by doing so JJ would admit to having drafted a bust. He also wouldn't want to run the risk of BB rehabilitating Carpenter, which would add to the embarassment.
I like Carpenter and it's a shame politics would get involved and prevent that deal from happening. A 5th is a good deal for a bench player.
BTW, I just noticed that Bryant McFadden cb, Steelers is an UFA next season. That is an interesting future option.