At the moment I don't see any young PSG academy players having a candidate capable of replacing Mbappe for now. One of the best ways is to take advantage of the transfer market by buying new players. Some media outlets suggest that Victor Osimhen, Rafael Leao, Bernardo Silva are reportedly new targets to replace Mbappe if he leaves. After he officially leaves, Enrique must be able to make a collective game, not rely on 1 player.
PSG is one of the big and richest teams in the French league, so it is not surprising that so far they often recruit star players at high prices rather than orbiting their young players from the academy, besides that it seems very rare that we hear if there are other teams interested in players from the PSG academy because maybe they do not have much natural talent to orbit young players like Monaco academy, Barcelona and Madrid at this time.
The absence of young players despite having a large academy certainly makes PSG only a team that does have a short-term vision, and of course it is very reasonable because indeed they can overcome this with the money power they have so far in recruiting players, losing Mbappe next season will certainly leave a big hole in PSG's front line, so that hole will be closed if PSG can find a player who can indeed be better than mbappe later, from Of the three names you mentioned, I think only Osimhen does have the capacity to replace Mbappe, while the other two will probably be Osimhen supporters in the future in PSG