Sea of Thieves will be receiving some major content updates over the next couple of months, with these aiming to address feedback from players. During April developer Rare will be working on ways to improve player encounters, and adding to the world. However, it is in May when a large content update will be dropped, and this update is called The Hungering Deep. The update will bring a new threat requiring crews to work together to unravel the mystery and to succeed.
Following on from The Hungering Deep two more content updates will occur during Summer with these being named Cursed Sails and Forsaken Shores. The first of these will add a new ship type while the latter will open up a new area in the world. Additionally, these will also have new threats to deal with, and items to find. Plans for pets and ship captaincy have been put on hold while Rare works on the other aspects of Sea of Thieves.
Source: Official Sea Of Thieves Site