I've said it before and I'll say it again, Pittsburgh would rather hold onto him than deal him for a lackluster offer. We see it every year- some team finds themselves in the thick of a pennant or WC race and can justify moving high end prospects for a guy like him (see Price; David).
Moving him for less than what they deem fair would be disastrous. If they didn't have faith he would rebound I think we would've seen him moved by now. I think (and I know I would) rather bet on a rebound and selling him at the deadline than moving him right now for a package around Devon Travis or someone to that effect.