Was just taking a wee look through Wowhead's 'latest additions' for items, spells and whatnot and came across an interesting set of weapons, all recolors of this gun.
What's interesting, aside from the awesome new model, is the title for them: Weapon - Firearm_2H_Rifle_Archaeology_D_01 - Black, also with appropriately named versions for Copper, Green and Red colour schemes.
While these all currently have no real implemented stats or proper naming, the brand new model along with its titling strongly hints towards archaeology getting a new weapon solve - in this case, a gun.
What's more, its appearance doesn't seem to fit either the Mogu or Pandaren, or even the Trolls - instead appearing to fit more with the Tol'vir or Nerubians...so a bit puzzled about that, and not really sure how and where it will fit in with what's going on in 5.2, if it does appear in 5.2 at all.
Anyways, now you're armed with this new knowledge, speculate away!