Sea of Thieves has gotten a lot of flack since launch for the lack of content found within the game, once you have done a few of each of the missions, you really run out of new things to experience. Rare it seems are aware of this, as they have detailed the road made for the next few months, letting players know that more is coming. The below developer video will cover everything, but it is long at almost 14 minutes, a shorter explanation can be found under it.
In addition, new mechanics and rewards will be added to the game, that players can earn when they take part in the event the new threat is apart of. This release will also add the weekly events to the game, giving players a a reason to return each week.
In the colder months, two additional packs will be released, Cursed Sails and Forsaken Shores, with the former adding in an entirely new ship type, the latter adds a perilous new section of map for players to explore. Similarly to The Hungering Deep, both of these updates will also include new gameplay mechanics for players, new AI threats to challenge and new unique rewards to claim.
Perhaps the thing that will please players the most is that all of these updates will be free.