The only way they would end up on Disney's service is if they toned them way down. Disney has said Play won't carry anything beyond a PG-13 level (the level of the MCU and Star Wars movies), and the Netflix Marvel shows are all TV-MA and way darker than what they appear to be going for for Disney Play.
It might not even be a case of "We want to move these characters over to our service", it could just be as petty as "We don't to hurt Netflix, because Netflix is the competition". As I said, Disney has grown very adversarial to other studios.