Okay so some copium of Wrath even coming back, but in the past bungie has stated that if a raid comes back that already has it's exotic in the game they would make a new one or bring an old exotic back that was from the same expansion.

Bungie has also recently released a twab announcing Buffs to caster frame Swords. In that same sentence they state "Caster frame Swords are our only sword archetype with a ranged attack(For now)"

This leads me to believe that when Wrath of The Machine does return the exotic will be Young Wolf's Howl, as this sword is from Rise of Iron and also has a ranged wave attack.

And with this Bungie may also make a new legendary sword archetype that creates waves of energy on the ground on heavy attacks.

That is my theory