There has been talk about a Joker origin movie for a while and Joaquin Phoenix has been pegged (rumored) as the lead. It’s rumored the film will be separate from the DCEU and be under a separate film label (and potential new universe) by DC Comics and Warner Bros.
No matter where it goes from here, I don’t think they can beat this awesome concept video compiled by Smasher. If you ask me, Willem Dafoe would make a spectacular Joker. Until I saw all these movie clips compiled, I didn’t realize how many insane characters he has played.