Bungie will reveal a pile of big news for Destiny 2 on August 24, 2021, but before they had the chance, a huge leak slipped past a partner's site.
Razer accidentally revealed that Season 15 of Destiny 2 will be called Season of the Lost and the image on the site also included a huge character return. If you don't want spoilers, you shouldn't go further into the article but Bungie will spoil it on August 24 anyway so it's up to you if you want to keep reading.
The returning character in question is the queen of the Reef herself, who was originally thought to have perished in a fleet battle with Oryx , the Taken King. Destiny and Destiny 2 players later saw her and had confirmation that Mara is not actually dead but in a different plane of existence. The artwork for Season of the Lost confirmed she will play a part in the story but it remains to be seen what will come of it.
Even though Razer jumped the gun a few days early, these leaks were present for months . Bear in mind that the linked thread contains even more story spoilers for the future, including the Witch Queen expansion and what looks like all of its seasons.
There are some leaks regarding Osiris' erratic behaviour as well. Many suspect him to be Savathun's pawn in the city and they are partially right. Once again, spoilers are ahead so think twice if you want to keep reading.
What we are seeing in cutscenes nowadays is a dupe - someone Savathun placed in the City and the real Osiris is kept somewhere else. The manipulative Hive leader will require Guardians to do her a favour in order to return the fabled Warlock.