The upcoming Green Lantern movie, Green Lantern: Beware My Power, can answer a major unanswered DCAU question. Granted, Beware My Power is part of the Tomorrowverse line of animated films and not the DCAU, so anything it does won’t reflect on the DCAU. Still, the fact that the movie will involve certain characters that are also featured in the DCAU means that anything it does can be seen as a form of payoff for that.
One of the many stories that was left unresolved when Justice League Unlimited—and the DCAU, as a whole—ended was whether or not Green Lantern and Hawkgirl would get back together. Even after betraying the League and the planet to Thanagar, John never stopped loving Shayera, and they both knew that they were likely destined to be together thanks to them having a son by the time of the DCAU's Batman Beyond. However, John wasn’t ready to get back together with her and didn’t want to do it just because destiny said so, and the show ended with them still broken up. The recent Justice League Infinity comic continued this by having John and Vixen break up, but he and Shayera still didn’t get back together, so the story still remains unresolved.
Green Lantern and Hawkgirl’s story was left unresolved, but Green Lantern: Beware My Power has a chance to fix that. While the movie isn’t canon to the DCAU, it still stars the John Stewart Green Lantern and the Shayera Hol Hawkgirl, just like Justice League and Justice League Unlimited did. Therefore, any sort of relationship the two develop throughout the movie can be seen as a payoff for leaving things unresolved in the DCAU.
Beware My Power could also work to give their relationship a better payoff than what happened in the comics. In Batman Beyond Unlimited, it was revealed that Vixen was murdered by the Shadow Thief on the night John planned to propose to her, which led to John murdering the Shadow Thief and being stripped of his ring. John and Shayera then rekindled their relationship following her funeral, which explains both how they got back together and why John wasn’t a Green Lantern in DCAU's Batman Beyond.
The major problem with Batman Beyond Unlimited’s explanations for John and Shayera’s relationship is how poorly it follows up on everyone involved. Instead of John having to make up his own mind about who he wants to be with, the choice is taken out of his own hands when Vixen is killed. Not only does that make his refusal to go along with destiny pointless, but it makes Shayera come off as just a second choice for John since it took Vixen dying for John to want to be with her again. While the comic isn’t explicitly canon to the DCAU, especially following the release of Justice League Infinity, it still does a disservice to all of the characters involved, so the DC animated movie has a chance to build a relationship between them without any similar problems involved.
As of now, plot details for Green Lantern: Beware My Power are sparse, so it’s unknown what sort of relationship Green Lantern and Shayera Hol will have in the movie. Even so, since it does feature John Stewart and Shayera Hol, that means anything done with them can be seen as a conclusion to their otherwise unresolved story from the DCAU. Whatever the case, it will take the actual release of the movie for any clear answers to be given.
