He has made a lot of changes in judicial and police posts to people he likes or follow his commands. And he is the fucking president, so what is someone realistically going to do to stop him.
He could modify the files, release them and get a massive popularity boost for being honest.
He could destroy the files and continue saying they never existed. This option seems a little too far fetched but still a possibility considering his overconfidence.
Considering how much shit FBI and CIA has got away with, it is quite possible
Yup, all they need is another Oliver Stone or Allen Dulles to throw under the bus.