Lionsgate did not immediately respond to a request for comment.
Australian filmmaker Patrick Hughes, who has a successful background in commercials, is directing the action-packed sequel, which Stallone is producing with Millennium Films.
According to insiders, "Expendables 3" will introduce a younger group of tech-savvy action heroes who initially clash with the older crew, though they eventually team up to save the day.
Also Read: Wesley Snipes, Nicolas Cage, Jackie Chan, Milla Jovovich May Join 'Expendables 3'
While Stallone has hinted on Twitter at the potential casting of Mel Gibson, TheWrap has confirmed that the "Lethal Weapon" star is not officially involved with "The Expendables 3" at the moment.
"The Expendables" films have grossed more than half a billion dollars, and the latest sequel will start shooting next month. "The Expendables 3" hits theaters Aug. 15, 2014.
Also Read: Kellan Lutz to Star in Millennium Films' 'Hercules 3D'
Since his breakout role in the "Twilight Saga," Lutz has starred in Relativity's "Immortals" and the Michael Bay-produced remake of "A Nightmare on Elm Street." He recently wrapped the title role in Renny Harlin's "Hercules 3D" and also stars in an upcoming "Tarzan" movie.
Lutz is repped by Innovative Artists, Zero Gravity Management and attorney Jeffrey Endlich.