Harley Quinn has been established as one of the DC Extended Universe’s main characters, having appeared in three movies as of The Suicide Squad. She’s developed from being The Joker’s partner in crime to being one of the saviors of Corto Maltese, although her future in the series is currently unclear.
This shouldn’t be much of a problem as previous movies have set up some potential arcs for Harley, while adaptations from the comics can allow the character to return in sequels and spin-offs. With Margot Robbie also willing to step back into the role, it’s interesting to speculate where Harley will fit as part of her next appearance.
Assembling The Gotham City Sirens
The Gotham City Sirens consists of Harley, Poison Ivy, and Catwoman, which would be a unique team-up to see in the DCEU. It would introduce the latter two supervillains to the series while placing Harley again in a scenario to assemble a female crew consisting of reformed baddies.
It would make sense for Harley to return to Gotham City after escaping Belle Reve, and with her departure from the Birds of Prey, Harley can be seen getting embroiled amongst characters with similar personalities to her. Considering Poison Ivy and Catwoman have their own issues with Batman, this team-up will be born out of their mutual experiences with the Caped Crusader.
Romancing Poison Ivy
The Harley Quinn TV series has taken off in popularity largely due to her association with Poison Ivy. Their pairing has also become romantic in the comics, with Harley realizing that The Joker really was abusive as a result of Poison Ivy accepting her for who she is.
Having fully moved on in The Suicide Squad after revealing to Silvio Luna that she was done with such romances, Harley's set to accept a DCEU love interest without giving up her self-worth. The story could see Harley being the one to reform Poison Ivy’s villainous ways and their partnership blossoming into something more.
Being Hunted By Peacemaker
The ending of The Suicide Squad confirmed that Amanda Waller intends for Peacemaker to do her dirty work now that Task Force X is no more. Since she can’t directly harm them due to Harley and her friends holding information against her, Waller can find a loophole by sending Peacemaker after them.
This can lead to an appearance by Harley in the Peacemaker HBO Max TV series, where the titular character will need to hunt Harley down. It would be an entertaining episode to follow, as Peacemaker will need to wrestle with his conscience against Harley, as he did the same with Rick Flag.
Meeting Her Fate During Darkseid's Invasion
Should Harley’s time be due for an ending in the DCEU, a good way to send her off would be to tie into the ending of Zack Snyder’s Justice League. Here, Batman revealed she had died in her arms and asked him to make The Joker pay for what he’d done to her.
To this end, Harley can appear in a potential Justice League movie where she puts on a last stand against Darkseid’s forces and goes out like a hero. It would close the circle of the setup from the Snyder Cut while completing Harley’s reformation that began from the first Suicide Squad.
Searching For Cassandra Cain
Cassandra Cain’s absence almost made no sense in The Suicide Squad, with no explanation over what happened to her. Harley had set up a business with Cain by the end of Birds of Prey and it only makes sense for her to return here after getting her freedom back from Waller.
Since there’s been sometime between Harley’s capture, it’s more than likely that Cain has gone her own way. With Harley having a bond with her, she can be seen looking for her partner around Gotham and running into trouble as she always does. This scenario could also be the setup for a sequel to Birds of Prey.
Facing Off With Batgirl
Batgirl is set to join the DCEU and her current arc is unknown. Harley has had a long-running rivalry with the superhero from her first appearance in Batman: The Animated Series, which can serve as an inspiration for the two characters to face off in live-action.
As Harley remains highly erratic, exploits like her destruction of Ace Chemicals Plant can lead to Batgirl tracking Harley down. This could place Harley as the villain for the Batgirl movie and would serve as a good way to introduce the character in the series.
A New Harley Through Flashpoint
An overhaul to the DCEU is expected in The Flash, which will depict the Scarlet Speedster entering alternate universes. The comics’ storyline had ushered in a revamped prime Earth where characters were different from how they were left off.
The DCEU can experience a similar event that paves the way for a different Harley than the one last seen in The Suicide Squad. The new version could be a full-on villain who hasn’t gone through the character development of the original in the DCEU, thereby preserving her earlier turn for the better while making the “Flashpoint” Harley Quinn closer to her comic book counterpart.
Flashback To Her Killing Of Robin
It’s not necessary for Harley to return in a sequel, as the cinematic universe can make room for a one-off appearance as well. It can be in the Batgirl movie or a feature that looks into the impact of the killing of Robin that was supposed to have been committed by The Joker and Harley.
It would show the character at her worst, which has only been alluded to so far in the DCEU. Should the series look into a Nightwing or Red Hood spin-off, the flashback can serve as Harley contributing to the superhero’s introduction.