The Wrap broke the story, which states that Evans is in "early discussions" about the film, but additional reporting from social media has risen the question of whether or not the film is part of the DC Extended Universe brand, or the DC Standalone Films brand:
in development, to be determined!— Umberto Gonzalez (@elmayimbe) October 25, 2017
DC fans had been excited to Joe Manganiello take on the role of Slade Wilson/Deathstroke in the DCEU; the actor was rumored to have a secret debut in Justice League, but was then speculated to be one of the main villains in Ben Affleck's The Batman. When Affleck dropped out of directing the Batman solo film, it quickly became apparent that Manganiello's role may be going with him; when director Matt Reeves took over The Batman, he brought a whole new story concept with him. The lack of any confirmation from Manganiello made it seem like the new version of The Batman no longer had a role for him, as he moved on to star in The Rock's Rampage adaptation.
This new bit of news certainly confuses the issue even further. If Deathstroke is a standalone, than it would be fine to introduce viewers to this version of the character cold; but if it's connected to the DCEU, making Slade Wilson's his first appearance in the shared universe be a solo film origin would be a questionable move.
One thing is for certain, right now: having Gareth Evans onboard is a definite win. Evans (not to be confused with Rogue One's Gareth Edwards) became a breakout star when his Indonesian martial arts film The Raid: Redemption road word-of-mouth acclaim to become an international cult-hit in 2011. The sequel film arrived in 2014, and while it was critically acclaimed for its brutal awesome martial arts stuntwork, it barely made a dent in the box office, and faded fast. Plans for a third and final chapter never seemed to come to fruition.
Evans may have faced a challenge creating a hit foreign film series with crossover appeal, but taking on a character like Deathstroke for a major studio like DC/WB seems like a match made in heaven. As Raid fans will attest, this will be a movie that brings a level of action that superhero fans have never seen before.
Stay tuned as more develops with this unfolding story.