Do not get emotionally attached to any character from the poster used for this article. In a recent interview from Empire, Director James Gunn clear said many characters will die. No one is safe. Harley Quinn may have the face of the franchise plot armor, but it is not the case. This movie is not a sequel to the first Suicide Squad movie. This movie is set on its own universe and continuity. This Motion picture have no relations with Justice League dceu universe and The birds of prey neither. DC comics and Warner Brothers had given the director of Guards of the Galaxy full liberties to do everything he wants. Gunn had worked with Warner Brothers before with the Scooby Doo movie and the videogame Lollipop Chainsaw. He have better relationship with them than Marvel and Disney.
Harley Quinn may appear in future DC movies but not even her is safe from getting killed of. A fan on twitter tweeted that Harley Quinn, King Shark and Amanda Waller are safe and 80% of the characters have a big chance to die. Gunn, responded to that fan:
“No character was protected by DC. They gave me carte blanche to do what I wanted. That was one of the things we agreed to before I came to work for them. I wasn’t looking for shock value but I wanted the audience to know anything could happen. #StoryReignsSupreme #TheSuicideSquad”
This statement further confirms he is given full creative freedom to do everything he likes. He could kill Harley in the first minute of the movie if he wants to. He wanted the audience to be on the edge of their seat. He wanted the film to be as unpredictable as possible. He have great past relationship with Warner Brothers so they gave him their full trust to handle one of their big franchises.