Not sure how this will go down, but one problem I see with extending the map is you end up with dead areas. Easiest way to grind OOS & Athena is in the Devils Roar so you find a lot of Legends there grinding away, which removes players from other areas.
I think if they extended the map further to incorporate the "Frozen Fangs" idea or added an Asian themed area you'd dilute the players more unless you upped the number of crews on the map but I believe increasing player numbers puts a strain on the servers.
So to get around this problem, you have a choice of 3 world maps to spawn into. The Original One, The Asian Isles and The Frozen Fangs. Each map is separate and you cannot swap between maps mid session, you'd have to come out of the one you're in and start a new gaming session selecting the map you want to play in.
I know the lore says something like "Pirates found their way to The Sea of Thieves through the Devils Shroud and this place exists on the actual world map." So how about adding to the lore saying that the same thing happened in other real world locations?
I know this would be a huge update but I guess the pressure on the servers wouldn't be too great because you're still dealing with the same map size and variables just a whole new group of islands and a whole new look to each map.
Each different world map would come complete with it's own set of challenges, tall tales & updates. Would you be able to use the same pirate for each map type or would you start afresh with a brand new starter sailor?
Perhaps you could "unlock" a map type after reaching Legend and then another once you're Athena Lvl 10. Each area could be harder than the last.
I am thinking whether you'd end up with entire dead maps, but with the size of the player base would that actually happen? Also if you made areas unlockable, new players would have to start on the original world. It may also divide player abilities making the newbie's experience a little easier.
As the core game mechanics would be the same from one world to anther, would this be such a hard thing to develop? You've got the sea, you've got the physics, so surely this would just be designing new looking places and introducing a selection panel at the intro screen.
I for one would love a brand new world map to discover and explore. Again, no idea how easy this would be to implement or if the affects would be really detrimental, but it is a solution to the "Map Extension" problem and finding areas becoming devoid of pirate life