I think Osimhen is a perfect striker for PSG and he will be useful for PSG even that team start a new season with or without Mbappe. With Osimhen, PSG will have a good striker who will bring many goals for their team and more than that, he will be able to support Mbappe (if Mbappe stays) and other players by his readiness to do proactively defense at the frontline.
If anyone needs examples for his readiness to do that, look at his performance in Champions League matches with Leipzig. Even when Napoli led with big goal difference, Osimhen still chased the ball around the box of Leipzig.
PSG must prepare a backup option if they fail to reach a contract extension with Mbappe and have to sell him in this season's transfer market, Victo Osimhen is the perfect option to replace Mbappe, his performance was quite consistent last season and he managed to become Napoli's top scorer with 26 goals from 32 matches in Serie A, proving Osimhen's capacity to be PSG's striker. But still dilemma with PSG current Mbappe situation unclear yet, not confirming about extend contract or not make negotiation for PSG signing new player faced difficult. PSG should have final decision from Mbappe extend or sell him in this summer window transfer before loss compete with other teams who in fighting race sign Osimhen.