That's right, Luis Enrique needs to recruit new players in the next transfer window to fill the positions left by Mbappe, Osimhen and Rahsford are worthy of being PSG main targets when the transfer window opens. Luis Enrique can update his strategy to suit the depth of the squad he has, of course it will take a little time to adapt. Meanwhile, PSG will continue to dominate Ligue 1 even though Mbappe officially leaves, they are too powerful for other teams.
If Kylian Mbappe really leaves the Parc des Princess, PSG will do it to find a potential replacement player. although in fact, currently Luis Enrique is building a potential team according to the version and style of play he wants from his squad. To be honest, I haven't really followed developments surrounding football lately. So, I'm just following what you posted. Well, I think Luis Enrique has several potential players for his squad next summer. However, if it is true that Mbappe leaves the French League, they will automatically bring in another player as his replacement.
As for the two names you mentioned in this post, Marcus Rashford and Osimhem are potential candidates for Paris Saint-Germain. however, I really doubt that these two players are willing to join PSG, because these players are also in demand by other elite teams. So if Paris Saint-Germain wants one of the two players, PSG must be willing to spend large amounts of money to attract the interest of the player they are targeting. However, if I had to choose from one of these two players, Osimhen is a more worthy player for Paris Saint-Germain to fill in as a pure striker. As for the Lique 1 competition, it will be difficult for rival teams to break the dominance of this French League giant team.