So, naturally, you’re going there to explore and set up a trading post because that’s what you do.
After you’re done with the mysterious island, you can hop back over to the continuation of the Hildibrand quests, which continue Nashu’s misadventures in Kugane with new faces, new complications, and presumably a new series of sight gags. You can check out the preview for a little more information, or you can just wait the short span of time until you can explore the content for yourself less than two weeks.
Source: Official Site