I find it extremely unlikely the plan going into 2017 doesn't include acquiring an impact bat for LF, either through trade or FA. The money is there (finally), and the trade fodder is there. I also find it equally unlikely that Maybins performance has altered the plan to acquire said impact bat in any way whatsoever.
If he isn't in the long term plans, then maximize his value. Keeping him may very well be the way to maximize his value, but I would bet flipping him to a contending team at the deadline would net a prospect more valuable than what Maybin will produce in the punting years. If no such trade materializes, or the team remains on the edge of contention, then obviously don't trade him just for the sake of selling high.