Napoli is not a favorite at all for the next season. They had a good performance this season and they won the title but since their coach and some players are losing this team I think they don't have too much chance for the next season.
It all depends on how the new Napoli coach will build the team's game, but in any case it will take some time and loss of points and this may be the reason when these points may not be enough in the fight for the Scudetto or even in the fight for a place in the Champions League. And yes, the loss of the head coach and rumors about the departure of players also do not make Napoli a favorite next season. So far, all the significant news and rumors about the team's people are on the way out, but there is no news about significant people in the team to enter.
Even if Napoli manages to keep their players in the team, there may be losses in their performance as the minds of the players may be on other opportunities. This will affect Napoli badly. Napoli is a great team and I'm sure they will work hard to win Scudetto once again with their supporters.