Over the course of this past year in Destiny 2, a number of fan-favorite exotics from Destiny 1 have made a return in the sequel such as Whisper of the Worm and Thunderlord. With that in mind, many veteran fans of the franchise are theorizing that perhaps the most famous exotic from the original game, the Gjallarhorn rocket launcher, may return as part of the game's upcoming Solar Week.
Currently, it is unknown when exactly Solar Week will take place in Destiny 2, as developer Bungie has only just hinted at its existence. The main evidence that Solar Week is happening is from datamined files from the game that fans have found that appear to confirm that it is coming at some point, likely during an Iron Banner week.
The datamined files describe Solar Week in similar terms to when Arc Week was active in the game back in April. And during that event, the game saw the return of the Thunderlord exotic quest that first debuted with the Festival of the Lost event six months prior. This has fans thinking that Solar Week will also have an exotic attached to it.
Another piece of evidence that is adding to the speculation is the existence of new items of some sort found in the same datamine leak described as "Scattered pieces of a greater whole" and "Rocket Launcher Components," which many are taking to be questline items. If these are tied to a Solar Week exotic quest, it seems to narrow things down to a rocket launcher. Despite a Gjallarhorn gag in the Thorn quest that made fans believe the exotic rocket launcher was returning, these new items look a bit more legitimate, making fans think Gjallarhorn could come back for real this time.
Lastly, fans are pointing towards August 14th as it is the fan-dubbed "Gjallarhorn Day," when Xur sold Gjallarhorn for the second time in Destiny 1, which allowed many players to finally get their hands on the powerful weapon in the original game.
Putting all this together, fans are hypothesizing that Solar Week will take place sometime in August before the September 17th launch of the Shadowkeep expansion. Because of the datamined files connecting the event to Iron Banner, that means it would likely take place at the end of the month if Iron Banner continues to follow its normal monthly schedule. Gjallarhorn is far and away the most famous solar-based exotic rocket launcher from the original game; however, there is also a chance that, if there is an exotic rocket launcher connected to the event, it could be the Dragon's Breath, the other solar exotic rocket launcher from Destiny 1.
Destiny 2 is available now for PC, PS4, and Xbox One.
Source: Destiny The Game Reddit