Speaking of Nagelsmann, I much prefer him over Galtier, Nagelsmann is a young coach who carries modern football. it doesn't matter what the French public thinks, but what is certain is that he has the capacity as a potential coach. that is why, Nagelsmann was targeted by several big clubs.
So far, there is only information that PSG is in talks with Nagelsmann, and this could possibly be a profitable deal for both parties, since PSG with Nagelsmann can become significantly faster, which they lacked with Galtier. PSG have good financial resources, so I have no doubt that they will be able to make a good offer. But first, we should wait for official information, because so far it just looks like a rumor.
I heard that on the news when they said Nagelsmann is going to join PSG for the next season and they think the reason of their team failed in this season was because of the bad coach they had.
If Nagelsmann gets better results in PSG I think Bayern Munich will feel regret.
It is very likely that Mbappe will remain for this season but Messi will surely leave, because I believe he has played his last match in the club. If Mbappe stays and they reinforce the team with good players that are not super star, the team will be balanced but congesting one team with 3 super stars.
If Neymar leaves, Messi leaves and 5 new and good players are added to the team for reinforcement, I believe PsG will have good results for the next season champions league.
So far the quality of Ligue 1 has not been able to compete with other leagues to reach the top of the UCL champions. It is evident, the power of money is still quite difficult to get a champion instantly. Neymar, Messi and Mbaape they are good but don't have hard work. It seems that they are too comfortable with a large salary. It seems that they have to change the mentality of the players to work hard. As for the League, they have had many titles. They just need to improve the quality for UCL.
In the next season when Messi and Neymar leave PSG, they will still have the chance to hire a better place and this can be a reason to say the quality of the French league won change.