Let's keep Atalanta out of the list. Look at their budget, and they have been consistently outperforming their rivals and pushing their ceiling higher and higher.
I don't think Lazio could challenge either. They had a good run before the break that masked their problems.
The only disappointment was Inter, who could clearly win it this time, but they failed miserably against the mid-table teams.
Next year, Juventus will be stronger with a midfield trio of Jorginho-Arthur-Rabiot, they could certainly play more 'Sarri-ball', and a striker upfront (Milik or Jimenez) better than retiring Higuain. Important signings (like Ndombele, Hakimi, Erisken already, a striker if Lautaro leaves) mooted or already completed for Inter, means Inter should be the closest again to challenge. But I don't think they can do it, if they failed this season.
Problem for Juve is they have Ronaldo, a player that does not fit Sarri's system. It was very idiotic from Anieli and their board to first buy Ronaldo and then hire Sarri. You either go with Ronaldo and a pragmatic coach like Allegri, or hire Sarri let him build and play beautiful football and sell Ronaldo.