A version of the Cir-El Supergirl will show up at some point in the future, quite possibly as a clone of some sort.
There are a few reasons for this theory. The first is the slightly added focus that the author has put on the Light's cloning capabilities relative to Young Justice canon, between Renka's musings on the subject, the rescue of Match, and the subplots involving the numerous other Cadmus clones such as Tora Drake. The second is the author's apparent fondness for building out the world and giving less well-known characters from the comics a place in the story (and while Cir-El isn't exactly obscure, she's by far one of the less popular and famous Supergirls). The third — and admittedly least compelling — reason is that the author has made a habit of fleshing out the Team's roster with female members to the point of it being lampshaded.In any case, if she does appear, it will likely either be as an Opposite-Sex Clone of Connor, or else simply a Distaff Counterpart to him as a half-human-half-Superman clone. With access to hemalurgy, the Light might even be able to give her Kryptonian abilities without the same issues that hindered Match. It's possible that she will be programmed with the same "Superman and Lois' daughter from the future" cover story she was given in the comics, but since the heroes are already wise to some of the Light's clone tricks that might be less effective than it otherwise would have been.
Renka will become a gold compounder.
Thanks to Death's nugget of Lerasium, Renka currently has the means to turn people into allomancers. While she's decided against becoming a full compounder like the Lord Ruler, she is the only feruchemist around, and as such the only one capable of becoming any sort of compounder, with gold compounding being one of the most useful types while still being hard to abuse if the League ever seriously needed to stop her. For one thing, as Word of Brandon has stated that gold feruchemy can heal damage to the soul in sufficient amounts, she might be able to use compounding to more completely recover from the aftereffects of Roanoke. Since she's also working on a way to temporarily share her feruchemy with others, she could also use compounding to build a stockpile of unlocked gold minds, allowing her to fill an important medic role.