Destiny 2's next piece of downloadable content is called Warmind, and will be out on May 8. More details to come via stream, as is Bungie’s way. Bungie also plans to change weapon slots and a whole lot of other stuff.
Bungie has gone into more detail about the 1.1.4 balance patch coming to Destiny 2 on March 27. A bunch of weapon types are getting PvE damage buffs, and several perks (including Kill Clip and Dragonfly) are also getting buffed.