11 Ways Suicide Squad Needs To Set Up Future DC Movies
6. Keep Harley Locked Up
It's pretty clear that there's an imbalance in the Squad's make-up, and a very different hierarchy of value (even narratively speaking) that distinguishes Harley Quinn (and probably Deadshot) from the likes of Boomerang and KIller Croc. She's money, they're mooks.
The worst thing Suicide Squad could do, in that case, is let her fly off free to do her own spin-offs without bringing her back for a direct sequel first. Without the MVP, a sequel would probably struggle, and though the scripters would have to find a way of dealign with the potential repetition (the Joker would inevitably come back for her again), it's worth the effort.
Suicide Squad 2 needs Harley in exactly the same position as she was (whether through force or by her own submission when she realises The Joker is worse than Arkham), so letting her loose to then recover her for a sequel is just a quick recipe for burning up unnecessary screen-time.
The Hints
If the Joker is looking for her, he's probably going to get his hands on her in some way, no matter how bad that will be for the sequel. Unless Batman's going to turn up unexpectedly to stop him in his tracks.
It's likely she's going to get away.