Story and Events up to... SPOILERS for new players. read at your own risk.

[archadria]

Things that have happened in the game.

Bandits have stolen the Rubber fruit from Sai the wealthy merchant.
The bandits sold that fruit to a mysterious hermit who lives in a creepy desolate forest cabin.
The island is populated by some Soul fruit users, strangely enough 2 of them lead different factions, Marines Captain Shotas of the Ice Fruit, and Lato Pirate Captain of the Fire Fruit. There is a 3rd, the frighteningly fast Frio po. another user who has no known fruit to date is Litorio, and strangely enough he knows about all the fruits in existance.

There was a war that devestated Rhum Island, Sir Loc was saved by one of the Pirates strongest allies. Kamel another soul fruit user will also teach much about the sad short story of Rhum Island. There was a hellish war here. The island barely more than a desert serves as a battleground to this day.

The marines have a fortress island nearby, the factions wage war over control of Rhum Island and Hajiwari.

This is what we know about our current sea.

Things we know very little about.
Dr. Megafunk, the greatest crafter, responsible for the design of notes sheets for improving weapons.
The Pirate Era, how Shotas became so corrupted and ate the ice fruit. How Lato took command of the Hajiwari Pirates, how he came upon the Fire fruit, how he got into dealings with the Hajiwari Marines.

Where to go from here?
In my imagination I see the next 2 conquests for the game being an "impel down scenario" because we have a marine fortress, this would allow another set of higher level mobs (above coyotes) to come into play. Possibility of new boss interaction, as well as Impel Down/Marine Fortress side quests.
The open sea, I imagine that Rhum Island, Hajiwari, and Marine Fortress are all in a small cape if you will. just a small percentage of what the open world is. I see the need for finding a navigator, someone who can use the log compass more proficiently than <the player> can use. Allowing the ability to leave the cape and traverse the ocean. The next need becoming a ship itself, whether the player can build a ship out of materials that are gatherable on the Islands, or if they have to steal a ship from the marines, or charter their crew a ship from a local merchant/faction.
Also as a side note, the "cape" as I imagine could be entirely out of possibility with open seas allowing the removal of the hit the steering wheel option on current ships.
Going even beyond the cape.
Aestetically we have a desert and a forest, plains and some plateues/canyons. What we have not seen is a sandy windy beach, some cold ice peaked mountains. A bustling city of crime and punishment. In lieu of open seas being a very large project, I would say that a large island with 2-3 tilesets being an upcoming area to adventure would be a wonderful way of opening up the world building. Mountain peaks, snow covered, with a certain being of lightning at the top, holding his throne for hundreds of years. A bustling city that has been overtaken by a criminal organization being funneled money by both marines and revolutionaries. Citizens in distress as local thieves guilds rob from the weak to help funnel criminal organizations. Deadly wolves in the snowcapped mountains, threats and myths of the Yeti or Bigfoot tribe. 
The feeling that most things in play are because of some shadow organization pitting pirates and marines against each other to seize all assets and control, the city being one of their more recent exploits. The cities Mayor/Chief/King being very obstinent that he is in control, asking <player> for help with information and removal of opposition parties. The mystery of whether the King is part of the organization pulling strings from the shadows, or a benevolent king. A tribe holding the coldest and most desolate peaks constantly at war with the city, marines, pirates, and the thieves, all while maintaining their tribes fight against the yeti and wolves.. just barely surviving with thier supposedly immortal chief.
The choices a player makes could wreak havoc on the island or save it.

[Shenmue]

Thanks for the ideas. Will make sure to implement some of them in the game story line haha. For example, Rhum Island, Hajiwar and Marines' Fortress being in a small cape is definitely something I want to do.
Also, next part of the game is probably going to be Impel Down or Sky Island

[archadria2]

Yes sir! 
wheeeee