The official release of Destiny 2's Shadowkeep expansion and the game's migration from Battle.net to Steam is just days away on October 1st; however, Bungie announced alongside the launch trailer for Shadowkeep that players can start pre-loading the game now in preparation. This pre-loading includes the Shadowkeep expansion and the base game, which comes in the form of the free-to-play Destiny 2: New Light edition.
Not only does that mean that those who purchased Shadowkeep on Steam can pre-load, but because of the addition of New Light, a large amount of the game's content that is free-to-play, anyone can start pre-loading New Light. Again, no part of the game will be able to be played on Steam until October 1st when Destiny 2 officially migrates from Activision-Blizzard's Battle.net platform to Steam.
Bungie community manager Cozmo also alerted current PC players that they will have to re-download the entire Destiny 2 client from Steam and that they will not be able to move files over from their install via Battle.net:
Cozmo also clarified that even players who pre-ordered the physical edition of Shadowkeep from Bungie's online store instead of directly from Steam should still download the base Destiny 2 client of Steam and then they will be able to type in their key for Shadowkeep once it is sent directly from the Bungie Store.
The change to Steam for the PC version of the game comes after Bungie's split from Activision, who served as the publisher of the Destiny franchise since the first game. Naturally, when Destiny 2 was released on PC in 2017, Activision-Blizzard's own Battle.net was used for the game. But now that Bungie is fully self-publishing the game, and especially with the addition of Cross Save in Destiny 2 that allows players to pick up their characters across any platform, the game is migrating to Steam.
Shadowkeep is Bungie's first step into its new world of self-publishing the game, and the developer has spent a lot of time over the summer assuring fans that it is looking to take the game in a direction that will appeal to the game's more hardcore players. That means leaning more into the MMO aspects of the game with more stats and a bold vision for the future of the game.
Destiny 2: Shadowkeep releases October 1, 2019 for PC, PS4, and Xbox One, with a Stadia version also in development.
Source: Steam