Chelsea will sell him somehow, but if they don't want to sell, they will rent him. Lukaku is now a striker who is of no use to Chelsea. If Napoli cannot buy, they can try to rent it for a year. Lukaku also loved Serie A and will continue to play there. I think if Osimhen does not leave and Lukaku comes, Napoli can have a more successful season than last year with a few good reinforcements.
It doesn't look like Chelsea will lower Lukaku's price, and of course it will be difficult to sell Lukaku at the value they want. Even though Napoli want him, I don't think they will want to spend a big budget to have Lukaku, so there is a possibility that they can rent him. Even though Lukaku's talent is already visible, of course as he gets older it will affect and reduce his performance as well as his own performance. If Napoli want to buy Lukaku, I hope they can consider it carefully so they won't be disappointed with their choice.
Napoli's goal in recruiting new players is of course their aim is to strengthen their performance, but they also have to think that if they recruit players they have to be able to adjust it so that they don't spend a large budget but the results don't match their own expectations. Whatever Napoli does, hopefully it won't reduce their performance, they must be able to play more consistently next season to be able to compete better than before.