The Black Armory, the first DLC in Destiny 2's post-Forsaken Annual Pass, is due this winter, and according to recent leaks it will add three fan-favorite Exotic weapons from the original Destiny, plus a new tier of gear. Note that Bungie has not confirmed any of this and that this gear does not appear in Destiny 2's API via sites like Light.gg. However, The Black Armory is explicitly about rebuilding the finest weapons ever crafted, which fits with the leaks.
The leaks come from two Reddit users with a history of reliable predictions: JordanWrightFilm and AnonTheNine, who in now-deleted Reddit posts (helpfully archived by YouTubers like Houndish) predicted the return of The Last Word, Icebreaker, and Thunderlord, as well as the addition of black-grade gear which is said to exist separately from Legendaries and Exotics. JordanWrightFilm and AnonTheNine disagreed on when these weapons will release, with initial reports claiming Thunderlord is part of the upcoming Festival of the Lost Halloween event, but many players believe the stage is set for their return.
Bungie confirmed a free update will add heavy machine guns to Destiny 2 ahead of The Black Armory, and Thunderlord, an Exotic heavy machine gun which grows stronger the longer you fire it, would make a nice cherry on top for the archetype. The Last Word, meanwhile, would sit nicely alongside the Huckleberry, Prospector and Chaperone, Destiny 2's other Tex Mechanica-made weapons. As a fast, fan-firing hand cannon which is lethal in close range, The Last Would would also provide a tidy answer to Destiny 2's now shotgun-dominated Crucible meta.
As strange as it sounds, the best evidence for Icebreaker's return is probably the mere existence of Whisper of the Worm, an Exotic sniper in Destiny 2. Icebreaker's ability to regenerate ammo was a constant source of balance issues in the original Destiny since it allowed players to sit back and snipe their way through many Strike and Raid encounters, most famously the Oracles in the Vault of Glass. This led many players to believe Bungie would leave the weapon in the past where it couldn't muck up Destiny 2's content. However, given that Whisper of the Worm is easily obtainable and also sports functionally infinite ammo, there's no reason Icebreaker can't have a spot in Destiny 2 as well.
Meanwhile, rumors of black-grade gear have been circulating since Forsaken leads Steve Cotton and Scott Taylor teased the possibility in a Q&A session with Game Informer back in July. More specifically, both answered black when asked what color they would use if Destiny 2 added a new rarity of gear. This fit with the name of The Black Armory, so players began to wonder if it was more than a hypothetical.
I visited Bungie's Seattle studio in August to play Forsaken ahead of its release, and I asked about the possibility of black gear during a follow-up panel with Cotton and Taylor. Taylor answered, and while he didn't confirm anything, he did break into a huge smile and excitedly say that Bungie "will definitely talk about that" closer to the launch of The Black Armory. You should take that with a grain of salt, but I won't be surprised if black gear is indeed a thing.
Apart from cautious optimism, these leaks have also generated some confusion because the original leak from JordanWrightFilm mentioned a new horde mode called Forges of the Chain and the first Last Wish raid lair. However, Bungie has confirmed that The Black Armory will indeed add a new raid lair, and while it didn't nail it down as a horde mode, the updated Destiny 2 content road map also confirmed Forges of the Chain.
Ahead of The Black Armory, Destiny 2 is getting new quests, activities, weapons and cosmetics in the Festival of the Lost.