The chance is always there for osimhen to go to the chelsea. As long as chelsea agreed to pay his clause release and osimhen will come to the stamford bridge. Napoli has been giving a green signal for any team who was interesting to buy osimhen from the club. Manchester united and chelsea have been rumored to be the strongest candidate to buy him from napoli. That depends on what kind if decision that will be taken by pochettino.
If pochettino still wants nkuku to be tested first and i think that osimehn will not become the main target by chelsea. Chelsea is really need number 9 right now. All of strikers owned by chelsea have no ability to play as real striker.
Let's wait what decision that will be taken by pochettino. Chelsea has not yet announced pochettino as a new coach. It may takes some time for chelsea to publicy it.
For a player like Osimhen, there are many other options he can have instead of Chelsea because we know Chelsea won't be in the next Champions League and even in the next Europa League, that's why there is not any reason for Osimhen to choose Chslea and accept their offer for the next season.