If PSG have changed their mind about Mourinho then Nagelsmann might be the one to take over.
PSG will take risk again if they sign with Nagelsman because the coach is very young and in a club with many star players like PSG, he will have to deal with same similar problems like what he failed to cope with in Bayern Munich.
People want to see Zidane managing PSG very much but I don't feel like this will happen. Because there isn't even a rumour I have heard of in the recent times. It looks like Zidane is still not keen on managing a team other than a national team he would like. If he signed for PSG now I would have nearly zero doubt left about PSG's future. Despite the solid players leaving the team one by one I would still believe in him to find a way.
Zidane has never shown his interest to be a club coach after leaving Real Madrid. He aimed at the French national team coach position and mostly got it but some last minutes changes from Deschamps and Fédération Française de Football break that opportunity for Zidane. He is a person with good patience so he will not give up that plan and take a job in PSG.
By the way I have also heard about Luis Enrique rumour. If we compare him to Nagelsmann he has a more impressive career surely.
Luis Enrique is a better choice for PSG than Nagelsman and I like this idea which is a rumor now.