It's one thing for Paris Saint Germaine to sign a world class attacker that'll serve as Kylian Mbappe's replacement at the club but absolutely a different thing for the person to become as effective as Kylian Mbappe have been at the club over the years. I don't think it'll be possible for the club to get a player that can be as prolific as Kylian Mbappe or have the same impact he used to have in the Paris Saint Germaine team. For the past six seasons, Kylian Mbappe haven't just finished as Paris Saint Germaine top scorer but also have been the top scorer in the French league in that same duration so getting a player that will register those same numbers of goals per season will not be possible for Paris Saint Germaine.
A good world-class striker will think long before accepting PSG's offer because PSG is not the best club in Europe and always has difficulty competing with top clubs that compete in the Champions League, so a world-class striker will also think that his future is only good in the domestic league because PSG has become ruler of League 1 for many years.
Moreover, it is not an easy thing for PSG to recruit a world-class striker because as far as I know it is quite difficult to find a good striker who has almost the same performance as Mbappe, so it is possible that PSG will recruit a striker who is probably still below Mbappe. At least that way all the players can help each other provide the best strategy.
Without Kylian Mbappe at Paris Saint Germaine, I know it'll affect their performance however, I'm of the opinion that they'll still continue to dominate French football because even in the absence of Mbappe, Paris Saint Germaine team is the the strongest team in the French league.
But most of PSG's performance so far is because of Mbappe's big contribution. If this player is no longer at the club, I think PSG will be on par with other clubs in League 1. So that competition between League 1 clubs will be even more exciting and we will see how difficult it is for PSG to compete with clubs without Mbappe. Many say PSG will still dominate League 1, but I still doubt that.