He struggled every year until this season. He was only given prospect consideration because of his draft position; he should have never had any shine.
Look, I'm not going to write him off, I'm hopeful that his success this year is permanent, but historically, unless you're Randy Johnson or Nolan Ryan, guys with control issues do not end up turning into good starters. The walk numbers look better this year, so maybe he's figured something out, we'll have to hang our hopes on that. However, that's not typically something that is fixed with young pitchers, usually they either have decent control or they don't.