Milan has always been a top-level team, now things with Modric will be on another level, for me Milan's game will improve like you have no idea, Serie A will be interesting because there are many Italian teams that are coming with everything, thanks to the Club World Cup the Italian teams that attended have a better budget, thanks to that they should take advantage of it like in the case of Juve, Inter, so in view of this things for Italian football will be much more exciting.
The hype of Serie A remains weak. Modric arrival and participation of Serie-A clubs in the Club World Cup won't make the Italian league as attractive as in the past. While playing in Serie A used to be a goal for players, that's now gone. Serie-A is not their dream destination, but they are prefer in La Liga and Premier League.
As for Milan, I'm optimistic they can compete for the title next season. While preseason isn't a guarantee of continued good form, I think Milan has a chance with their current form if they can maintain their consistency.