In a recent Instagram post, Lucie Pohl (voice actor for Mercy on Overwatch) posted a selfie of herself near a recording microphone. However, hidden in one of the corners of the photo is this:
I know you can't see the full first word, but what else could it be? That says 'DUNGEON BOSS'. No denying it. So, either Overwatch is going to add a new game mode called Dungeon Boss (which would actually bring you guys into this anyways due to copyright issues), or she's voicing a new hero for Dungeon Boss (ya know, the grunts and giberish and all that).