DC and Warner have announced a lot, and I mean, a lot of Joker-related films. There's Jared Leto's Joker in Suicide Squad, the Joker meets Harley Quinn crime-horror-romance-whatever, and then the Joker origins film slated for 2019 with Joaquin Phoenix as the Clown Prince, which will be released in a new banner of DC original films.
We can't tell the future of these films but DC and Warner are experimenting here on a number of stuff. Should the Joker origins film be a success - despite DC's current track record - it could set off an entirely new genre. Instead of a "Superhero movie" what we might be getting will be a "Rogues' Gallery movie."
It would be the antithesis of a superhero movie. We will get to explore the origins and backstories of the most popular supervillains, without having them to clog up most of the main hero's movie. It would also be a way to humanize these supervillains and show us their side of the story. An origins of Sinestro, for instance, can better show viewers why he would eventually betray the Green Lantern Corps to set up his own elite Lantern club, along with a better introduction of Abin Sur, before Hal Jordan meets him.
If DC manages to pull the Joker movie off, expect the avalanche: Catwoman, Two Face, Deathstroke, Lex Luthor, Sinestro, Ra's Al Ghul, Lobo, Vandal Savage, among others. Black Adam has already been confirmed with Dwayne Johnson attached to it. The New Gods have been confirmed as well, which should give us a good hype buildup of Darkseid and Apokalips.
With a villain's origin story out of the way, there's better screen time between the conflict with the hero. Christopher Nolan's The Dark Knight is the perfect example, where Joker's backstory there is shrouded in mystery, leaving many details vague. What it did instead, was explore Joker as a threat to Gotham City, armed with a handful of gasoline, while engaging Batman in the philosophies of morality and nihilism.
In any case this should be something to watch out for. Personally, the DC villains are far more interesting than the superheroes themselves -- except Wonder Woman, she's The Badass of the Badass in DC.
For now, let's look forward to the big Aquaman reveal in the San Diego Comic-Con 2018.