User blog comment:Master Sima Yi/Assassinews 03-03-'13 — Assassin's Creed IV: Black Flag trailer and screenshots/@comment-5019018-20130306165435/@comment-4868246-20130306183613

Actually, AC3 was the first to implement stealth mechanics, the previous ones had poor stealth. However, if you're referring to social stealth then yes, it did deteriorate :)