If PSG have changed their mind about Mourinho then Nagelsmann might be the one to take over. 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.
I think Zidane is not something that is just "fan favorite" type of deal, it's literally the best option they will ever have and that's why people want to see him. Remember, this is the dude that won UCL 3 times in a row, who else can say that they did something like that, it's a singular achievement that is unique in any angle.
This is why PSG being managed by Zidane is not just a want, but also a need. If they can somehow get him, then they are going to be getting everything they will ever need. On the other hand, I agree that it's not going to happen and I believe Nagelsmann would be the only one left for them to hire but that's not going to be enough if you ask me. They aim at being one of the best clubs in the world, and in order to have that you need to have one of the best managers in the world.
There is no way Zidane is going to manage PSG knowing that he is probably not going to find huge success. If he is actually going to take a managerial job, I believe it is going to be in Real Madrid again or probably any other team in English Premier League. He's not going to go to same club which basically does not have any competition in the league itself.
Nagelsmann can be a good choice for PSG. But again at this moment, managing PSG is not easy because the expectation is to win the Champions League title, which is obviously the hardest trophy in the club competition to win. But it can also be a fan experience for a new coach because he is going to have access to a huge amount of money. But he will have to show some success.