But the winter transfer window will be irrelevant for him. There is no chance whatsoever that Napoli would let him go because for what reason should they do that? The transfer fee will still be the same in summer and I doubt that Napoli needs money this winter so urgently that they could not wait until summer. He still has a contract and the situation for Napoli wouldn't change. It would still be the same negotiations and I think clubs would be willing to spend more as this fits their budgeting and it is the time when they also let other players go and make their plans with potentially a new coach for the upcoming season.
There is some information going around that he has a clause in his contract, which says the fee would be well over €100m if someone wants to buy him. But still a winter transfer is off the table. Anything else would be shocking as they are still playing in the Champions League and they would tremendously weaken themselves if they sell one of their core players. But it won't happen as I said before. The tasks they have in front of them are too big to make such a dumb decision now.