[Update #2]: Skull and Bones has been delayed yet again, though this time we have an actual release date - March 9th, 2023!
[Update]: Skull & Bones has been delayed for the fourth consecutive year, this time around until 2022-23.
After the success of Assassin's Creed IV: Black Flag it became obvious that there is considerable interested in a fully-fledged pirate game. As such, it really shouldn't come as much of a surprise to hear that there are now two multiplayer pirate adventures just beyond the horizon: the cartoony and stylized Sea of Thieves, and the much more serious Skull & Bones from Ubisoft themselves.
If you're wondering how exactly Skull & Bones improves upon the foundation set by Black Flag, and more importantly of all, how its actually going to play, you'll find your answers in the official "What You Need to Know" video. The whole thing is fairly long, but it does a rather good job of explaining what Skull & Bones is all about, so I'd recommend having a look despite its length:
Those snippets of information aside, I'm afraid there isn't much else when it comes to concrete details. But if you would like to learn a little bit more, or just check out some of the other gameplay videos, you should head over to the official website. As for the release date, you can expect to see Skull & Bones in the Fall of 2018 on PC, PS4, and Xbox One. And since I can offer you little else, allow me to send you off with a couple of images: