Leaving in the winter means giving up the Serie A title that Napoli is close to getting and ending their Champions League run since you can't play for two different clubs in the same Champions League season. I think zero players are interested in this option even if they are offered a triple salary. They'll just wait for the summer. Sometimes illogical transitions happen (like Casemiro to United) but I don't think that will happen to Napoli players who are title hungry.
After this world cup we are having winter transfer window which is surely going to be vital for many teams and players as few teams are trying to secure quality players for next season which is their strategy but here many players definitely will not love to leave their clubs those are involved in Champions League because leaving club mean early end of season for them into Champions League which is never been ideal situation.
There are few speculations for few players those are interested to leave their clubs and want to join better clubs with better salary, but hopefully things will be happened in summer transfer window specially for Napoli which is currently at the top of league table and currently doing amazing job in both competitions they will be definitely not allowed any movement which will harm their strategy for the better end of this season.
I expect this is going to change the look of a few teams. And Napoli should be careful about that. Even though I do not think that they need any changes right now in the team, they should still think about the weaknesses that they probably have and bring in a few players just for safety.
This is so that, even if they suffer a serious injury, they are still able to perform well and won't have any problems regarding that. I do not think Napoli is planning to make big changes, to be honest. But I do think that probably Milan and Inter are looking to bring in a few players. I wonder if any Italian league team is interested in Cristiano Ronaldo!