“Big changes are coming to Destiny 2. With today’s announcement of Destiny 2: Shadowkeep, developer Bungie has a new way to deliver content to its players. When the major expansion lands on on September 17th, the core game will go free-to-play, shifting to “expansion-level, standalone content” for Destiny veterans.”

Source.

Moving free to play, the game will be called Destiny 2: New Light and will include all year one content : “foundational modes, activities and rewards.”

The game seeks to lure gamers away from other free titles like Fortnite

The game will stay free and additional contents will be made, like Shadowkeep.
Last year, the game was given away for free for a short time but it required the players to have bought the game to have access to newest contents.
The game will bring more cross-platform support. A cross-save feature will allow players to access the same character from their primary account from different platforms.