Maybe they will add them in an artistic/stats way though (like what Asylum mentions) where they could have a blade on a rifle and it would increase physical dmg for skills like butt stroke/ect.
Of course, you can pickup special buttstroking gear too. Affixes that provide extra buttstroke damage/effects, such as "Concussive Polished Gunblade of Iron", Concussive adds 25% chance of a 3 second stun when you use buttstroke, and Iron adds flat damage to the buttstroke.
Lol, getting carried away here. :P