After watching Inter this season I think the other teams will really need to make a huge progress this summer. 
Because the gap is just enormous now. Maybe you will say Napoli were also like this in the prior season and failed later on. However Spalletti left the team which caused big problems to start for Napoli right after.
There isn't such thing for Inter. They are moving on with Simone Inzaghi. I believe they have the best squad in the league at the same time. In this situation it wouldn't be seeing them winning a back-to-back title unless we see some reaction from another team.
Last season Napoli was truly extraordinary. They also did the same thing as Inter Milan did this season. But Napoli was unlucky because at the end of the season they had to lose their mainstay coach, Spalletti. And this has made Napoli really chaotic this season. And they could only finish in 10th place. Napoli's mistake was that they couldn't retain their coach who brought Napoli to a good level last season. And when Napoli lost the coach, it was natural that the team was no longer as strong as the previous season. Because the gap is just enormous now. Maybe you will say Napoli were also like this in the prior season and failed later on. However Spalletti left the team which caused big problems to start for Napoli right after.There isn't such thing for Inter. They are moving on with Simone Inzaghi. I believe they have the best squad in the league at the same time. In this situation it wouldn't be seeing them winning a back-to-back title unless we see some reaction from another team.
Meanwhile, Inter Milan doesn't seem like they will lose Inzaghi. Because reportedly, currently many foreign teams are targeting the Inter Milan coach, Inzaghi. but reportedly Inzaghi may be closer to staying and signing an extended contract. And this is good news for Inter Milan, which can still be expected to remain as strong as this season.