Brain "Fodderboy" Taney has offered up a lengthy dev blog detailing what's next for the nautical MMO, and he outlines two main goals: immersion and the desire to "layer" the game.
Immersion is fairly self-explanatory (and in case it's not, Taney says that it entails bringing more authentic 18th century elements to the game). Layering requires a bit more verbiage, but it basically boils down to improving "the game experience for all the different kinds of players we have in our community (e.g., casual, hardcore, PvE-only, PvP-only, etc.)," Taney says. There's quite a bit more, of course, but you'll need to head to the official PotBS website to read about it.