Jason does spend chunks of time with Frank Carroll in CA taking jumping tech with him, I don't think Frank would be a decent full time coach for him though, and Tom Z is definitely not a good fit.
He'll never leave Kori IMHO.
Could you see Jason working with Alex Ouriashev, or would that just "muddy the waters" at this point with Jason having to unlearn what he has learned with Frank?...Can't imagine Jason changing coaches. He has said Kori was his first coach and would be his last coach.