Warner Bros. has reportedly staked out two new dates for what are being called "event films," which generally means large productions with big name actors and directors attached. According to a tweet from box office analysts Exhibitor Relations, the dates claimed are September 27, 2019 and February 7, 2020.
Stop the presses! UNTITLED WB EVENT FILMS are now set for 9/27/19 and 2/7/20.— Exhibitor Relations (@ERCboxoffice) October 12, 2016
While not impossible, it's unlikely these event films are related to DC Films, as Warner Bros. has historially made a distinction between its DC dates and its other properties.
Either of the dates could be an addition to another existing tentpole franchise the studio has, one of the many rumored Harry Potter spin-offs, or they could be new projects such as the recently announced Oceans 8, which, as Exhibitor Relations pointed out in a follow up tweet, was also billed previously by Warner Bros. as an "event film."