Osimhen's price is too high for a team like Ac Milan I don't know where the idea comes from to say Ac Milan trying to hire Osimhen for the next season but as far as I know, other teams in Serie A can't have enough money to hire this player for the next season and even if Napoli gets some offer for Osimhen from other teams, there will other teams like PSG with better financial situation.
But regardless of that, I think Napoli's first priority is to keep Osimhen for another season.
Ac milan is not really interested in recruiting Osimhen there is not even an issue linking them if they want to recruit osimhen in this transfer window. I agree with you that the high price of Osimhen will make the Serie A team unable to bring in Osimhen in this transfer market. For now only the teams from the Saudi Arabian League have strong finances to recruit Osimhen from Napoli.
For now Al hilal is trying to seduce Osimhen in this transfer window where Al hilal has made a bid of 140 million Euros to bring Osimhen from Napoli. So, if Napoli accepts this offer, it is very likely that Osimhen will play in the Saudi Arabian league next season. But i think he will consider accepting the offer from Al Hilal because he is still quite young and can pursue his dream in europe with another team like PSG.
Napoli is still ok this season as Osimhen's contract is running until 2025. But when Al-Hilal made that offer, did Osimhen say that he would go to Saudi Arabia? Napoli can keep him for another season and they don't really have to fear to be missing out on a sensational transfer fee. That would still be possible next season. But for Osimhen signing a long-term contract with a club from Saudi Arabia would put any of his title ambitions on ice for a very long time or even forever. Going there at the age of 24 would be a brave decision as this really means a decision against a top level career. He should give himself a couple more years in Europe.