If you haven't been playing The Division 2 you really ought to, as it is an absolute blast to play and looks gorgeous too (check it out here in our extensive The Division 2 Benchmarked: 20 Graphics Cards Tested article).
The Division 2 developer Massive Entertainment has announced that the Tidal Basin update drops on April 5, with the first post-release content providing the Tidal Basin stronghold mission and World Tier 5. Tier 5 is The Division 2's hardest difficulty, and also packs the highest level gear. The new stronghold is held by the Black Tusk faction, which you would've battled in the game already.
You can also repeat strongholds you've already captured so that you get new loot, and fight your way up to the harder Heroic difficulty mode with gear that goes up to 500. Battling Black Tusk enemies will see them dropping new gear sets including True Patriot, Ongoing Directive, and Hard Wired.
Massive Entertainment has also promised that the new Tidal Basin update will be the first large-scale balance to The Division 2, something that is definitely needed. The new Tidal Update is the first of many new post-release content for The Division 2, with 3 more coming later this year.