No doubt, Osimhen is a good player. Osimhen is among the top 10 strikers in the world right now. But when a club gets a new coach, the first thing the coach will do is to assess his players to see the ones that will not fit into his tactic so that he can get a replacement immediately to enable him to perform well. Already, Conto wants to bring Lukaka to Napoli, which I think will make Osimhen want to leave the club to sign for another club where he will be a regular starter.
Even before this decision of bringing in lukaku, isimhen has always wanted to leave Napoli, except if he's now of a difference opinion because of the arrival of conte , obviously it looks like with conte, a lot may get to change and will probably get to help osimhen fit in well with the teams strategy and forms, I think it's even a better and good idea if osimhen would want to leave because there isn't assurance in the fact that he will be able to work fine with conte.
Lukaku isn't a better striker when compared to osimhen, by my personal opinion, osimhen will stand as a better choice if placed side by side with lukaku but then it's really lays within the confines of the coach to choose exactly who he finds fit enough and good for him to work with as a coach that he is, I may see osimhen to be a better striker but the coach may find it easier and better to work with conte. Napoli is looking to me like a team that will experience a very good improvement by next season such that they will be able to contend to get back the title they once held.
Leaving Roma will be another challenge Lukaku will have to tackle and I don't know if there have been any official statement in that regards as to him leaving or the team willing to selling him off to any other team willing to buy him but the transfer windows are still open so let's see what happens after now, if conte will succeed in bringing lukaku from Roma to Napoli.