Ya, Trump has been on the verge of making the switch to a competent and sober professional so many times now that it's incredibly fucked up that people continue to hold out hope that it's something that will happen.
Kelly will, of course, try to manage him but then Trump will get tired of being managed after a few days and do something outrageous and stupid just to demonstrate that he doesn't like it when people try to manage him. Then everybody will act all surprised that this happened because they really thought he'd turned a corner this time.