I don't know if Pogba will leave but I really want him to leave because he would always want to leave and there is no use keeping an unhappy player and also, there are too much weakness in his game. He's obviously talented because he's highly visionary but his weakness needs a lot of work.
First, his work rate and stamina is something that need to be worked upon, which I doubt could be improved because he's got this langiud laid back style which makes him suitable for the no 10 role (similar to Ozil) however his first touch interplay, agility, movement and speed of thought are not as good hence why he keeps hovering between the no 10 and central midfield role. He's neither a no 10 nor a central midfielder.
Secondly, the weakness I already touched upon which are first touch passing interplay skills, movement and quick speed of thought are also needed in the midfield to control the tempo. Pogba's first instinct to have a feel of the ball before making a pass and his constant love for punting long ball into open space for a runner can only be effective in a counter attacking France setup which had Mbappe as a runner on the wing. If he was a no 6, it would be understandable (I actually feel he plays as a no 6 for France).
But to be able to control the tempo in the midfield as a no 8, a midfielder needs much more than just long passes. His speed of thought must be quick and must always be the right decision and also, he must always be on the move to help to keep the play moving through his passes and movement and also, provide options with his movement and position in the midfield.
Lastly, he should be able to make quick first touch vertical passes into open space in between the lines unless the middle is packed up hence the need to quickly switch play to the wings or make a long pass whenever an opportunity opens up for one however It's not just about making long passes like Pogba loves to do. I have watched Pogba many times and his first touch interplay are just not good enough. Even when he's not making his trademark long passes, his first touch vertical interplay is a bit slow, average and not zappy enough to keep the play flowing. So also is his movement. Obviously, he's not been helped by having a coward in Herrera on the pitch who hardly provides option while Pogba's on the ball and would rather hide until we're no more in possession but still, Pogba needs to do better. He's got talent in other areas such as his creativity/vision and passing range which are good however he's a bit of luxury to have in the midfield and need the midfield to be just perfect for him.
Since he wants to go to Madrid, I would love if we could use him to get Ceballos from Madrid. Let's say 100mil + Ceballos because Pogba would always want to leave like he's been singing all through the season hence it's better we start preparing for a life without him. While Ceballos doesn't have the passing range of Pogba, his first touch vertical interplay is one of the best. Likewise his movement and workrate. He's been much more daring while he's with the Spanish national team than with Madrid where he often withdraw into his shell, probably scared of making mistake. If we could bring in both Ceballos and Van de Beek into the midfield, we already solved our issue in the midfield because they are both incisive, good first touch passer and have got good work rates capped with Tonali at the base of the midfield.
I did a comparison stat with Ceballos, Pogba, Matic, Herrera and Van de Beek (His 2017/2018 stat when he was deployed as a no 8) (the eredivisie is obviously a weak league though but at least the stat shows us what he's capable of.