IF we went by the initial plan the Justice league movie 2016 was the first part of the movie if it had been Snyder cut but it was completely changed by Joss Whedon,
And Since Zack Snyder left the Justice league mid-way, the DCEU has gone downhill and the tough completion for the MCU has made the situation worse.
Joss Whedon’s Justice League is till now the worst performer int he box office among others.
The major reason has been too much use of CGI, excessive dark-theme and uncertain and irregularities in the storyline and lack of back-story or character attachment with the audience.
If we went by the Snyder cut then the main villain for the sequel was supposed to be Darkseid which was again supposed to be established in the former one. but since the plan is all turned upside down.
now if we go by the mid-credit scene of the released version then the big bad was going to be the injustice league headed by Alexander Luthor and Slade Wilson AKA. Deathstroke and there was a plan to add one or to more members in the justice league by introducing the shazam family and rest.
There was also an idea to introduce the green lantern crop. in the movie so that they could establish the watchtower scene with all the main characters.
but as of now the whole movie has been packed and kept in a deep dark secret valve in Warner Bro’s office.
As the movie hasn’t been officially announced yet so there is no confirmation who all are returning to play their previous role,
if it happens at all Henry Cavill, Gal Gadot, Ezra Miller, Jason Momoa, and Amy Adams can hopefully return
still, now no announcement has been made and moreover, the Warner Bro’s are focussing more on the stand-alone movie as of now.