Gotham Knights creators Warner Bros. Games Montreal has confirmed a couple of villains that'll be present in the game so far including Mr. Freeze and the Penguin, but so far, we don't know for sure if Harley Quinn will be in the game or not. Some recent gameplay shared by the game's official Twitter account, however, indicates that a Harley Quinn appearances seems more likely than ever before.
The gameplay in question didn't focus on Harley Quinn or any other villain but instead examined Batgirl and a slice of her moveset. The video below shows Batgirl descending down to the streets of Gotham using her cape before assailing enemies with various strikes and combos while weaving in some dodges between the attacks.
This gameplay clip is brief and moves quickly, and if you're looking for Harley Quinn in it, you won't find her. However, the goons Batgirl is fighting have a distinct look about them that appears to mimic the red and black attire Harley Quinn is best known for. The enemies' outfits are made up of those exact colors, and they appear to have white makeup on their faces, too. Combine all that with the fact that one of them seems to using a baseball bat as a weapon and you've got pretty much everything about Harley Quinn except the character herself making an appearance in the clip.
Though Harley Quinn is often seen working with the Joker as opposed to running things herself, this clip combined with past info shared by the developers suggests that we may see her in a more autonomous role in the Gotham Knights game. The devs recently confirmed that Joker would not be in the game at all but wouldn't definitively say whether or not Harley Quinn would be in the game. That more or less confirmed plans to include her somehow, and if these are indeed her thugs seen in the clip, perhaps she'll indeed have a strong presence in the game.
A big villain reveal is coming soon regardless, so Gotham Knights fans can look forward to learning more about the game's antagonists in the coming weeks.