I think zidane is the perfect coach for a team like psg and if he join i don't think mbappe or any other player will leave the club, zidane is a great coach and everyone will surely wish to be under his supervision, psg administration must do everything to convince zidane joining the club
The problem is that Zidane's willingness to train PSG is not yet there, so that has not happened until now, even though the PSG administration can still persuade Zidane at this time to train PSG. And it would be extraordinary if PSG were able to bring a coach like Zidane into their team the following season. But I still have doubts about this because I remember the will of Zidane himself, who may not yet be there to train PSG.
Before Galtier there were clear rumors about Zidane but at the end there have some internal issues which prevent him from doing this like PSG management having different levels of treatment to players which are not acceptable for any good coach and then few other issues were also preventing top rank coaches for having spot here but as things are going right now we can expect good changes specially as right now we have management is ready to take few tough decisions then we can expect something better because discipline is most important for the success and if PSG management will bring these changes then surely we can expect good results in Champions League as well from them even few top players will leave this club but still they are capable of doing better.
With nothing is clear who is going to leave and who is new going to join, most chances we will have new coach in summer and how things will be for this all we have to wait for some more time about this all.