Born with the name Slade Wilson, Deathstroke is an expert assassin with super strength and stamina.
Affleck recently teased some Deathstroke test footage in a short video on his Twitter account, see below.
— Ben Affleck (@BenAffleck) August 29, 2016
There's no official Batman release date yet, however, Warner Bros. Pictures still has some placeholder dates tied to untitled DC Entertainment releases on the schedule (specifically in 2018 and 2019). Seems like 2018 is likely given the early footage or unless Deathstroke is making an appearance in the currently filming Justice League, the Zack Snyder's superhero teamup film set for November 17, 2017.
Manganiello, who recently married actress Sofia Vergara, will next be heard as the voice of Hefty Smurf in the upcoming 2017 animated film Smurfs: The Lost Village.