The problem about Chslea for both players, Gavi and Osimhen is both players are attractive targets for many other teams but regarding Gavi, I don't think if Barcelona will lose this player easily because they have an 18-year-old player who can have a shining future and Osimhen can have much better options than Chelsea.
It's better if you see the situation that happened with gavi. It's very easy to say that barcelona will not let him go but if barcelona has not solved yet its financial condition. Barcelona has no ability to prevent him from leaving from the club. Osimhen may be going out in summer as long as there would be a good offer for napoli. Napoli already priced him so high at this moment. His chance to leave from the club is even bigger since some rich clubs are targeting him right now. As long as these clubs have money and they can send bid for osimhen.
Newcastle has been starting to send bids for him but napoli rejected them. It seems like that second offer from newcastle will be coming to napoli. So many clubs are putting their attention to the osimhen right now but the only club that will able to send huge offer will get him.
As long as newcastle will increase its bid to 150 millions and napoli may accept such offer. It can be considered a really big offer for osimhen.