Mbappe is a very special player. His place will not be easily filled. There will be very few players who can achieve the success he achieved. If Mbappe had left two more seasons earlier, Messi and Neymar would have been more important players. But Mbappé is the key player this season. Mbappe's absence will affect PSG badly, but Enrique is certainly thinking about it. I think he has already chosen the player to replace him.
Even though it is not easy to fill the position left by Mbappe at PSG, Enrique still has to think about this for the sake of his squad next season because PSG will have to fight even harder next season due to not having Mbappe in their squad anymore. But just to compete in Ligue 1, PSG is still the best even though Mbappe is no longer there, but the problem is when PSG plays in other leagues such as Champions, which will make it more difficult for them to compete next season.