They aren't even sure Dunning is physically ready to pitch half of a season yet. I'm not saying he is or isn't, but he wasn't called up because they thought he was ready. IMO he will possibly get the call next year if they dont sign a FA and Lopez cant figure it out, but they'll probably wait till at least July
Edit: Forgot about Rodon. yeah unless we trade away one of Lopez/Rodon I dont see Dunning getting many if any starts next year