Those expansions aren't going to sell themselves! For a limited time, Bungie and Activision are giving away Destiny 2for free on PC. All you need to do is log into Battle.net and you'll see a prompt for a free gift. The promotion is set to run until Sunday, November 18, so there's plenty of time to partake.
Clearly, the idea is that you'll become invested enough in the base game to want to pay for the DLC. On that end, Bungie is also planning to hold a free trial for the PvPvE mode Gambit. That promo will run from Friday, November 9 through Sunday, November 11. It's one of the highlights of Forsaken.
If you have any trouble securing your free copy of Destiny 2, note that Bungie is requiring new users to set up Blizzard SMS Protect before they can get their free game. (You hear that, bots?)
Finally, current Destiny 2players will earn an exclusive new emblem on December 4, 2018 to "commemorate the first anniversary of being on Battle.net." I'm so glad I didn't double dip!