You are right that Osimhen is not interested in extending his contract with Napoli. This is why Conte is not interested in Osimhen now. He wants to add Lukaku to the squad. Because Napoli management will try their best to sell Osimhen this season. By selling Osimhen, Napoli management will earn a huge amount of money.
Osimhen is talented. He has managed to score a lot of goals in the last two seasons. Several big clubs like PSG, Chelsea, Arsenal and Manchester United are interested in adding a talented player like Osimhen to the squad. However, 130 million euros is a very high price. No club is interested in spending so much money. If it is 75-100 million Europe then maybe Napoli management can sell Osimhen this season. But the Napoli management is not interested in selling Osimhen for less than 130 million euros. Osimhen's future is still completely uncertain.
Napoli's management is too selfish to charge a high price even though Osimhen's quality has seen a decline in last season. Of course no team would be willing to buy him at a high enough price, except last season after Osimhen succeeded in bringing Napoli to win the Scudetto and Osimhen performed quite well.
Maybe the issue of Osimhen's transfer will become a hot drama in this transfer market, but whatever it is, I'm quite sure that he will leave Napoli.