If the whole world is going to be included we talk about thousands of ports, millions of navigation and sea marks that is going to be placed according to real nautical charts + dozens of landmarks, cities, towns, facilities, bridges etc. I wonder if you have any idea how long it will take to make that wish come true...
Besides of this the game engine will also have to be re-programmed so you have "seamless" world travel from one place to another without getting a "loading scenario" screen with a loading bar.
And if the sim is going to be more friendly for night navigation in the future then that just add a new mass of work. But who knows...Microsoft can always start to look this way when they now have a Train Simulator that is based on the FSX engine. I can imagine that they in the near future CUD make a ship simulator on the same engine. But they would have to collect a lot of information for all the ports. Because I think it's more ports and harbors in this world than airports.