If we consider the resumption of the championship as a restart, then Napoli should not experience problems, since the first half of the championship is always successful for them. The problem is that it will be an "unusual" start of Serie A and different players will be in a completely different state after the break (those who rest will be retrained and those who play will be tired). Everyone will need an individual program to get back into Serie A games again. But I think Napoli's medical/therapeutic team can do it.
Napoli will not worry about this to start Serie A when the world cup is over, surely the players and coaches will have time to polish their players again to keep performing well in training sessions before the competition starts. Yes, there are indeed a number of teams that will be a little overwhelmed in dealing, especially if the players are injured in the world cup. however, Napoli this season has been quite consistent in every game so when the games start again I think they will be able to maintain their positive trend, but one thing that can make them lose control if several Napoli players choose to leave in January later, of course this is very detrimental to Napoli if they have to lose core players in january.
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.