Rare has announced the first of six major free content expansions for Sea of Thieves, all due to arrive before the end of 2018.
The first is The Hungering Deep and it sets sail in "early May". The developer is being coy about what, exactly, will be involved in this first new adventure other than revealing it introduces a new enemy to the game that must be found and destroyed as part of a special event. New gameplay mechanics will also be added to help you in this task.
Two more expansions will drop in the summer, called Cursed Sails and Forsaken Shores, adding a new ship type, a new map area and more new gameplay features and rewards. There'll then be another three major updates before 2019 rolls around. Also incoming are weekly in-game events, designed to keep the game feeling fresh in between these larger evolutions.