We got the great news last Friday that The Killing Joke was finally being adapted into an DC Animated Feature with Bruce Timm as one of the Producers, no word yet on if he is also writing or directing.
It was also reported during the panel in between the two showings of Justice League: Gods and Monsters, that Bruce Timm was asked if he had been working with Tara Strong on anything lately and he did confirm he was, but refused to say what the project was for.
It would certainly be a change in the story, unless they make it that she is the wife he lost in his head or something as the character had not yet existed within Joker’s world when Alan Moore wrote the story. This is called an adaptation and in today’s world many see Joker and immediately ask, “Where’s Harley?”
Keep in mind this is speculation on the moment based on information given to ComicBook.com. Tara Strong could be voicing Raven in the Justice League Vs Titans film that was announced earlier as well.