Napoli last season was relatively consistent with Spalletti, but with his departure, hopefully it won't be a season sensation for Napoli even with a new coach. Because next season it will be more difficult to win and it is possible that the chances will shrink if the competitors are able to improve well at the end of the season until the start of next season. If you can return to performing consistently, it shouldn't be difficult for Napoli to at least finish as runners-up and it is possible to win again.
De Sanctis tends too choose good coaches for Napoli so let's hope that he will continue to do so. Napoli will have a second season with some big changes and they just surprisingly succeeded in the past season with some departures of key players. It will be hard for them to repeat such success if they lose star players in this summer again.
Don't let things ever happen in the Premier League like Leicester city won the English league and now they are relegated. Hopefully Napoli can learn from them by not selling star players, even if they do sell them they have to get a commensurate replacement.
We can not say it will never happen but I see difference between Leicester City and Napoli. Before winning Scudetto in this season, Napoli had about 10 years of good performance in Serie A. Leicester City did not have same position like Napoli before their sudden successful season with Ranieri. Napoli seems to have good transfer strategy and salary policy that will help them in long term. It can be changed if De Sanctis will resign as a President of their club but we will return to discuss about it if he leaves.