Napoli will need to keep their squad unchanged if they want to continue their good form and win the title. Napoli are playing well because the understanding between their players is very good now. Also we see good performance from Napoli in every match due to their good match strategy. If any of Napoli's key players leave the squad in the next winter transfer window, it will have a negative impact on their overall performance.
They will not want to sell their players in January and changes can come from injuries by World Cup or very high bids from super rich clubs. Most of clubs are not ready to spend too high budget for January transfer market. Star players don't want to change clubs in middle of season too.
Napoli will need Osimhem to return without injury then they can give him one or two matches for resting, to recharge energy and to avoid unnecessary injury after all. They do need contribution from the striker, not only by his goals.