Having an abundance of good catchers is never a bad thing. You can always trade one for a missing piece somewhere else. Look at the Rangers. They've got at least 2 catchers in their system I'd rather have over Bako/Ross/Valentine. The Mariners have at least 2 I'd take over Bako/Ross too.
Posey has demonstrated he can play any position, so he's not totally locked into catching, IMHO. If he's there at 7, I hope the Reds take him.