User blog comment:Master Sima Yi/Assassinews 03-03-'13 — Assassin's Creed IV: Black Flag trailer and screenshots/@comment-161.50.48.2-20130305015403/@comment-4868246-20130305154942

The creative director actually elaborated on this point and explained who they will rehabilitate the assassination mission structure from AC1, were you have the target and that's it, the rest is up to you :D

He baisically stated that there will be no more hand holding or restrictive design, allowing you to exploit the environment to your whims :)