User blog comment:Master Sima Yi/Assassinews 03-03-'13 — Assassin's Creed IV: Black Flag trailer and screenshots/@comment-24.199.83.66-20130311001215/@comment-2142534-20130311144055

They probably started making naval warfare for AC3, and when they noticed they could add more to it, but not until the AC3 release, another team started working on the next game (AC4) which will have more focus on naval. And that would have happened in 2011. Also, the best period for keeping the naval system from AC3 is the Golden Age of Piracy. So yeah, you are probably wrong.