Releasing Victor Osimhen and having new striker is normal as we are now having new coach at the Napoli after having worst end of the season which bring too much decline in quality and having no consistency after winning title with this all happen due to management level mistake which bring serious trouble and team gone in deep trouble after this all, but now they are working to bring back themselves at the better spot which they deserve in Serie A.
Antonio Conte and Romelu Lukaku have good relationship while these both already work and achieve better results, so things can take good change here as well. Romelu Lukaku is having good depth in last few seasons with he can shine under Conte here at the Napoli which could be good for them because we can expect better results and improved performance which is also important for them for having success.
Although there have been no comments about Antonio Conte deciding to replace Victor Osimhen with Romelu Lukaku, all this speculation is born out of the Belgian's good relationship with the coach. Another reason why this speculation is high is because Napoli will make money from the transfer of the Nigerian and they really need the funds. The new coach will want to overhaul the club which means they will need money to buy new players.
Lukaku has had a good season, but any club that relies on the Italian striker for goals will not get the best. Osimhen had an average season because the team was not organized and he also suffered some injuries. Lukaku cannot be compared with Osimhen if the Nigerian is in a good team. Victor can be relied on as a striker because he is still young and strong, so I don't see any point in comparing the two strikers. It will be a good move to try to convince the Nigerian striker to remain in the club. But it looks like he has made up his mind to leave. Conte can use his connections in Chelsea to secure a money-plus player swap deal so that the Nigerian can move to the English side while the Italian will secure a permanent deal in Napoli.
You are very much correct on this one here, the best and the more favourable thing for Napoli to do is to try to convince the Nigerian star attacker to stay put, because in as much as his possible replacement Romelu lukaku is very good, he is actually not an upgrade to victor osimhen, victor osimhen is more younger, stronger and has more years ahead of him that romelu lukaku, though Napoli needs to do more in trying to convince him to stay, but if they think it's worth it, it's best that they give it a shot.
I know that Antonio conte would want to overhaul the squad, which is a logical thing to do especially when the team is coming out from a terrible season, but I don't think it would be that much, because they don't have the financial power to do it on that scale, so I think that their will be changes at the club, but not that much.