All the Destiny 2 expansions are free to play for the next week

As of right about now you should be able to access every currently available expansion for Destiny 2, for free. As the base game is also free so that means you can play any campaign you have missed, plus the most recent three Episodes.
Bungie are clearly hoping to lure back players before the launch of The Edge of Fate, the start of a brand-new story within the game that will take players to the planetoid of Kepler.
The Edge of Fate will take place on Kepler, a new destination inspired by the puzzle-solving and pathfinding challenges of Destiny 2’s dungeons and destination design which encourages deep exploration, mystery, and player-driven discovery,” say Bungie. “New enemies, weapons, gear, and destination-specific abilities await those brave enough to dive into its secrets.”
“A key feature of Kepler is the abundant dark matter energy, which powers the destination’s abilities. The new Matterspark ability allows Guardians to bind to dark matter to change forms, enabling them to squeeze through tight spaces, jump and dash across terrain, and become a rolling force of destruction. Additional abilities include the new Relocator Cannon, which uses Fallen dark matter tech to teleport players across the environment, and Mattermorph, which lets Guardians manipulate their surroundings using the combined forces of dark matter and Strand.”
The launch of The Edge of Fate will also see a huge – and I mean huge – number of changes to the game itself. UI, armor, vendors, infusion, currencies, even your power level is changing as everyone will be reset back to what you started in Destiny. Yes, Destiny, not Destiny 2, you’re going back to power level 10.
There will also be a new Raid launching on July 19th and as usual there will be a contest mode to begin with which will be extra difficult and only for the most seasoned fireteams.
Source: Bungie