Losing Mbappe would cost PSG really a lot by the way. He is like their everything at the moment. In his absence I don't know how consistent and powerful PSG can be. They have made a good transfers for the future maybe but these new players will need to take their time to adapt and improve their skills to create a solid team.
In case of Mbappe's leaving maybe PSG would look for a solid replacement for him. But for now I don't know who they would go for. Maybe Haaland? Because his release clause is expected to be active by this year so we never know what PSG will do after that.

TBH, it is very difficult to see Mbappe leaving PSG, but only in this way can the PSG team become more independent without relying on just 1 player. I mean PSG has always depended on Mbappe for a long time, whereas a team can be said to be very strong if it has solid players without relying on just one player and I also really understand that PSG actually wants to win the title in the UCL but is not strong enough to only rely on one player even though he is a striker does not mean he is the only one who has to score and other players also have to play an important role in scoring.
we can see, for example, Man City in the UCL, even mainstay Haaland didn't score in the final round and Real Madrid didn't just rely on Benzema at that time.
well, this is the reason I say that the time has come for PSG to be independent and learn to become a more solid team and be able to win titles in any competition even without Mbappe. I'm sure PSG can be even better.