Nothing is known about the plot as of yet, but Henry Cavill's second standalone Superman movie is planned to be directed by George Miller (Mad Max franchise, Mad Max: Fury Road).
Director Jon Schnepp was promoting his documentary The Death of Superman Lives: What Happened? when he let it slip. He's had inside access to Warner Bros. and DC Comics in putting together his own movie about the failed Tim Burton and Nicolas Cage superhero adventure. Warner Bros. is reportedly so happy with the success of Mad Max: Fury Road, that they have decided to reward George Miller with the job of directing Man of Steel 2.
Zack Snyder was set to direct Man of Steel 2 for release in 2015, but those plans changed as the sequel morphed into Batman v Superman: Dawn of Justice, which hits theaters spring 2016. Zack Snyder will then direct Justice League Part 1 and Justice League Part 2.
Jon Schnepp was pretty confident in his claims that George Miller is directing the Superman sequel Man of Steel 2. This shouldn't be viewed as an official confirmation though, and the studios have yet to weigh in.
Jon Schnepp makes his comments around the 55:30 mark:
Source: Movieweb