My only worry is the lack of quality talent in defense once Chiellini and Bonucci hang up their boots
Defenders will step up imo. Not really worried about that. We'll have Bonucci and Acerbi for a while, Bastoni is one of the best young CBs in the world already.
Romagnoli or Mancini can fill in if no one steps up as a top talent. Maybe Lovato will be the player.
The big worry is as always the striker. After Immobile there are only uncertainties. Scamacca, Raspadori, Kean, Lucca, Esposito, etc. are all talented but until they make the jump it's only promises.