DC Collectibles revealed last week that they are releasing a 3.75" Harley Quinn action figure based on the upcoming Injustice: Gods Among Us video game.
No word yet on if this will be part of some hard to find set or convention exclusive or other ridiculousness, but I'd bet on it not being easy to find. Because I want one, and DC toys I want are notoriously hard to find.
Although this is DC Collectibles, not Mattel, so maybe there's hope.
In the meantime, check out this Injustice: Gods Among Us gameplay video featuring a battle between Wonder Woman and Harley Quinn (along with a surprise appearance from some other Bat-villains from an entirely different video game!)