For a game that was supposed to be released prior to the end of 2018, it sure seems that Skull & Bones is taking a long time in development. It's so delayed, in fact, that Ubisoft announced that it will not be seen until "financial year 2019/2020" which means April 2020 at the earliest. In addition, Ubisoft also announced that the game will be skipping this year's E3. These announcements were made during the Q&A session in Ubisoft's investor call earlier today.
Skull & Bones first came to the attention of the world at E3 2017 complete with a cinematic trailer and a demo that had a lot of naval combat fans pretty stoked. The game is in development by Ubisoft Singapore and there is a Skull & Bones television show that is also in the works. It's unknown if it will be delayed as well.