It's reported Martin Scorsese is involved and also that Leonardo DiCaprio is wanted for the role of the Joker - as this one won't feature Jared Leto in the role - with the movie being directed by Hangover's Todd Phillips.
Now it's being said that the Joker origins movie script is already complete and being sent to WB, as a reporter for Variety tweeted out the Joker script is being turned in next week with it suggested the movie may start filming next year.
Hear THE JOKER script will be turned in by next week, super fast considering when announcement went out bodes well for 2018 shoot— Justin Kroll (@krolljvar) September 20, 2017
As noted, it seems as if Warner Bros. is fast-tracking the Joker origins flick.
Further details also include the Joker origins movie has been said to be "super dark and real," with the Joker "as a kid, he had a permanent smile and everyone made fun of him. It’s like on the streets of Brooklyn."
WB is also developing a separate Joker movie for Jared Leto pairing him again with Harley Quinn; Jared Leto also said to be appearing in Suicide Squad 2 and the DC female villains movie, Gotham City Sirens.
It does seems as if the two different Jokers could cause confusion with the general audience, but apparently WB will be giving the brand something to set it apart, perhaps calling it "Elseworlds" like in the comics or something similar.
A Superman "Red Son" movie has also been pitched to WB, which would obviously be a part of the new DC standalone brand. Matt Reeves' Batman movie may also be potentially a part of the different branding of DC movies.