They have to pick up the Miley option, whether to keep him or trade him. It would be malpractice to let him walk. I'd lean toward keeping him as you can't assume perfect health in the rotation. My take is Miley gives them a bridge arm while they work in Greene/Lodolo. The kids are going to have a learning curve. You want too many competent arms as opposed to not enough.
FWIW, I don't think they can get a lead pipe cinch OF for Miley. The kind of team that would be trading for a veteran arm who costs $10M isn't going to be moving a quality bat in the other direction. The Reds might be able to get an unproven guy they like, but they probably can get that for less prominent price.