I predict none of them turn out WC. Berardi, Rugani, Coman probably have the potential, although Coman is still a little young to decide that... Sturaro and Zaza don't have the potential to be starters at top 10 teams in Europe, bench options, sure, not starters. So of the three that have potential to be world class, safest bet is that not a single 1 turns out World Class, as you're probably looking at World Class meaning top 5-10 in the world at their position depending on strength of the position. The number of 20 year olds with world class potential is probably 10X the number that actually turn out world class in reality.
My bet. 2 decent-good starters. 1 bench player. 0 world class.