Napoli have fallen far behind so it will probably not be possible for them to get back into a good position again this time. The way Inter are playing makes it much easier for them to become champions. Inter are ahead of the other teams on points, so it will be very challenging for the other teams to overtake them. Napoli didn't focus on their performance early on which is why they are in the situation they are now. So I can't consider Napoli as likely to do anything good ever
Now Napoli is also starting to be chased by other teams such as Fiorentina after the Fiorentina team won in their home match today and Napoli's own number of points is also the same as Fiorentina. So Napoli are now really feeling the pressure to maintain their position in the top four of the standings and must be able to do something to stay in that position during this season. Because this season it will be very difficult for Napoli to get a trophy like they got last season, but at least Napoli can get a top four position so they can enter the UCL competition again next season.
Yes indeed, I believe there seems to be no more chance for Napoli to be able to defend the Scudetto because yes, with Napoli's current situation that is not entirely good. Moreover, it seems that Napoli's new coach is also not entirely appropriate to overcome the problems experienced by Napoli at this time. Therefore, it will certainly take time for Mazzarri to be able to provide a good performance for Napoli and it is unlikely to happen quickly either.
Therefore, because other teams besides Inter are still difficult to maintain a good trend then yes, at least at this moment Inter have a good chance of getting the Scudetto. Perhaps, it's too soon to predict the teams that will win the trophy as there is still the next half of the season. But, for now it seems pretty clear and I recognize Inter have been the best in Serie A so far this season.