Bungie already announced Season of the Chosen pass will have a Tex Mechanica Exotic quest but data mining provided more details about the weapon.
When Bungie revealed the next Exotic quest from the season pass would be from Tex Mechanica foundry, pretty much everyone thought it would be The Last Word's big brother, The First Curse, that made an appearance in the first Destiny. There were a few solid indications this would be the case, the current 120 RPM HC meta being chief among them.
It was not meant to be though as data mining confirmed. The weapon in question will actually be a Scout Rifle, named Dead Man's Tale. This information is coming from a dump made by GinsorKR who has a long history of data mining Destiny 2 content successfully.
He also dug up an image of the weapon, which you can see on the image above, but it's not the base appearance. The ornament features a few wraps around the rifle which are not everyone's cup of tea so let's hope the base appearance has more wooden parts instead.
One particularly interesting part about the rifle is that it appears to be a lever-action weapon, which would give us a unique archetype to work with, if it's indeed the case.
Furthermore, the fact that it is a Tex Mechanica weapon probably means it's going to be in the Kinetic slot since the vast majority of their firearms use the good old gunpowder as opposed to fancy space magic and energy rounds.