The important change that PSG must make next season is the strength to reach the final in the Champions League and also try to get their first Champions League trophy next season. Because if they are only too busy with the Ligue 1 trophy, I think PSG will still be considered an ordinary team and not better than other teams that have won the trophy. Mbappe's departure to Real Madrid could indeed be a very hard blow for PSG, but that is not the only reason for PSG to remain strong with their other players next season.
It is very difficult for Paris Saint Germain to win their first trophy in the Champions League, it is something that is not easy and perhaps even requires luck if they want to get their first trophy in the Champions League. They are indeed strong, but their strength only dominates in domestic competitions, while if they are in the Champions League, their strength is not that great to be able to compete with other teams which in my opinion have an even better mentality than Paris Saint Germain.
Moreover, we will have an increasingly stronger Real Madrid next season, they will have Mbappe and that adds to the strength that Real Madrid has. Honestly, I don't expect Paris Saint Germain to be successful next season, even though the opportunity is still open, but when compared to other teams, they don't have a bigger chance than other teams. Unless something big happens to them, like for example they perform very well next season.