Expansion I for Destiny 2 has already been detailed, thanks to a listing spotted on the Microsoft Store. Called Curse of Osiris it will introduce a new playable location, Mercury, and will introduce new story-missions to tackle adventures - aka Destiny 2's version of side-quests.
As per the listing here are the details.
Destiny 2 Expansion I: Curse of Osiris continues your Guardian’s journey with all-new story missions and adventures set in a new destination, Mercury. Journey through time and space to learn the secrets of Osiris, avert a dark future, and rebuild the ties between the legendary Warlock and his greatest student - Ikora Rey.
We're still in the process of reviewing Destiny 2, but it's great to see that the first Expansion will feature a lot of new stuff.
In other Detiny 2 news, the game has also hit an impressive milestone 1.2 million concurrent players.