Assassin's Creed IV: Black Flag will include multiplayer, of course. That's a given.
However, it will not feature naval-oriented multiplayer modes, which many fans may find disappointing. They're not the only ones who are disappointed, though: Creative director Ashraf Ismail "lost a lot of sleep" making that decision. That's what he said during a PAX Prime panel .
He said Ubisoft created multiple prototypes for naval multiplayer, and that the scope was "really huge." But it seems they just couldn't make it work correctly, and they weren't happy over losing that option. As Ismail lamented:
"It really broke my heart the day we decided to cut it from the game."
That all being said, if Black Flag does well enough, the next franchise installment may feature a naval multiplayer mode. Ismail added that history is the realm of Assassin's Creed and a futuristic entry probably isn't in the cards. Those who love the meticulously designed worlds found in past AC iterations probably appreciate that. I know I do.