Announcement by Kevin Smith and Zack Snyder for the Snyder Cut's Red Carpet Premiere Event. March 17, 2021, at 8 PM PST on Twitter/Facebook/Youtube/here, whenever they have an official link.
Check out this trailer comparison mashup between the original theatrical "Joss Whedon Cut" trailer for JUSTICE LEAGUE from 2017 with the latest "Zack Snyder Cut" trailer.