Osimhen must move to a team that can offer him the chance to win trophies. I doubt if he wants to move to Chelsea although Chelsea can pay him more expensive than other teams. Chelsea is just a mediocre team in EPL, Osimhen won't expect any trophy with Chelsea.
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.