For next season I still favor Napoli and Inter Milan but a little doubtful about Inter Milan regarding the issue of fixed matches. Do you see potential for other teams to catch up to these two teams? in my personal opinion, there aren't any yet, because I use the transfer window as a reference.
For the first few weeks, Juventus, AC Milan, AS Roma and some other contestants will probably be competing closely with Napoli and Inter Milan in the race for the Scudetto. Napoli seems to be stronger among the other contestants because Conte is staying, besides they are also actively adding strength by recruiting experienced players like De Bruyne. However, let's see first how other Serie A contestants complete their plans in the transfer market, as you said, it can be a reference to assess how ready they are all to face the challenges in the next season. Inter Milan don't seem to be as strong as last season, as they have parted ways with Simone Inzaghi.
Serie A teams have started preparing for next season and I think it is very difficult to predict now even though some top teams are still favored but don't forget that Juventus and Roma are developing teams that are certainly targeting to win the Scudetto next season.
Many people may doubt Inter Milan because they recruited an inexperienced coach but I will not look at that lightly because anything is possible, especially since the squad in the Inter Milan team is quite good so they also deserve to be taken into account.
And for Napoli, of course, they are the main candidate even though it is difficult to maintain the Scudetto, but we can see that the steps they are taking now make the team stronger, especially with their plan to recruit Kevin De Bruyne, this is quite beneficial for the team.