Warner Bros. has had a Hell of a time getting The Flash up to speed so it can hit the silver screen like all of the other Justice League solo movies. The film has been on hiatus since losing its second director, Rick Famuyiwa, over "creative differences" and who knows when it will eventually see the light of day. Certainly it will be a further away now as Variety reports it is getting a complete rewrite.
Basically, The Flash is starting over from scratch with screenwriter Joby Harold (King Arthur: Legend of the Sword) hired to give it a go. What all of this means is that there were some seriously deep problems with the previous versions, which were penned first by original director Seth Grahame-Smith and then by Famuyiwa. The only things that seem to remain are Ezra Miller as The Flash, Kiersey Clemons as Iris West, and Billy Crudup as The Flash's father. If things keep delaying I doubt any of them will be able to stick around.
Fortunately, Miller has a gap in his schedule to shoot Fantastic Beasts 2. If The Flash isn't ready to roll after that all bets are off.