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.
Real Madrid has money and they are willing to pay with expensive price to the player they want including Osimhen and indeed gets Osimhen is Real Madrid backup plan because if Real Madrid failed to gets Mbappe or Halland this winter then they decide to switch their target to Osimhen and indeed according to the news Osimhen was ready to signed new contract and it says if Osimhen and Napoli reach an agreement then Osimhen will be at Napoli until 2028 and he has 130 millions release clause into his new contract
This news indeed still uncertain because previously Osimhen was linked to some of Premier league teams just like Chelsea or Manchester United and Osimhen too has been says if he want to leave Napoli then he will give his priority to the premier league teams this because Osimhen was really interested want to play at that league but Real Madrid is a big team and they are as the most champion for Laliga and champion league so it's hard for Osimhen to refused this team if this rumor is true