First of all, Osimhen's contract with Napoli runs until 2025. It won't be easy to transfer him before 2025 because he is one of the best along with Mbappe and Haaland and the Napoli president rejected all offers for him in the summer transfer window. However, according to media reports, if Real Madrid can't sign Haaland or Mbappe, they will try to sign Osimhen as a plan C. I think this is a possible scenario because Real Madrid need to sign a striker of this class. So, I think there will be many alternatives for Osimhen in the transfer window. Everybody wants to sign a striker like him.
Unless a club wants to redeem the release clause and perhaps the fee will be quite high even though Osimhen's contract expires until 2025. Real Madrid's focus may be much greater on Mbappe, but it is possible that they will try to influence Haaland to move to Los Blancos. Manchester City probably won't let Haaland leave because he is an important asset for the club now, so it is likely that Mbappe will be much more likely to be brought in by Real Madrid than Haaland in the upcoming transfer market.