I think PSG will be fine if Mbappe really goes to another club, because currently Enrique has no shortage of good players in his squad. I admit that Mbappe is a great player and has technical qualities above the average of other players, let's say he is a typical player who can make a difference for the team, but I don't think PSG management is building a team that is oriented towards just one player.
For some time PSG will certainly need to adapt, adjust to being without Mbappe, and it is possible that they will be a little unstable. But on the other hand, we also shouldn't ignore the talents of other players who could be a solution to Mbappe's departure, who knows, PSG will be more solid without the star players who are prioritized by the club, getting preferential treatment, big paychecks, and potentially causing jealousy in the locker room.
PSG priority is winning the Ligue One title and also taking home the UEFA Champions League title which comes first on the radar list. PSG performance doesn't decline, rather it keep streak winning in league matches and they're top club and won't be allowing any poor results to draw them back. Luis Enrique and the president of Paris Saint-Germain, Nasser Al-Khelaifi who's desperate to pin Kylian Mbappe in PSG, he's going nowhere other than focused on his contract to run out before he would take his decision to exits Parc des Princes stadium.