Spoiler:
Darkseid is the JL villain, obviously. The first movie ends with him being teleported elsewhere and the League realizing they need to recruit even more (see more about that later) to stop him when he returns.
Superman is absent until the very end. He comes back and delays Darkseid just enough so they can send him somewhere else.
Batman and Superman have some nice back and forth banter. Seems kinda out of place though
Willem Dafoe is playing Kent Nelson. I saw the helmet the other day on set. It's on Kent's shelf in one scene. They're planning on suiting him up fully for JL Part 2 (more on that later).
The second Justice League film will have many of the lesser known League members joining up. They want to create a huge team of members to include whenever there is a global threat. That way, fans can get hyped and hope that they bring in the rest of the League for future movies. Other heroes they're considering now are Blue Beetle, Zatanna, Martian Manhunter, Booster Gold, Plastic Man, Raven, and some others.
The only hero brought in for Part 2 that stays a, main member is Green Lantern, who will be Hal Jordan (John Stewart might appear briefly in Part 2, still discussing that).
The Cyborg movie is up in the air right now. Lots of talks about making it into a Titans film instead.
Zack Snyder is NOT being booted off any upcoming movies. I've seen a few petitions online concerning that. Everyone I've talked to about this knows about it and is worried about this movie. Snyder is focusing on visuals again but the story is way more coherent this time in my opinion.
The Justice League Dark movie is NOT dead at all. I heard they're going to have a huge announcement about it at Comic Con this year. The goal is to make everyone forget about Marvel this year and reel people back in after the failure of BvS.
Martian Manhunter is a big character they're considering bringing in, but they're worried the general public will think it's too weird or not like him. They're considering changing his character up a bit to fix this, but I don't personally like it.
Lex does get cleared. LexCorp pays someone else to confess to blowing up the Capitol and provides the needed evidence to clear his name. He makes a speech claiming he will clear his name in history and show the world he is a good man. He has a very small part in JL, with his speech and the news story shown for a few minutes
The villain in Wonder Woman is Ares. He has some freaky Scarlet Witch level mind control that he uses to kickstart World War I (if I'm not mistaken, he mind controls Gavrilo Princip). Ares is a longtime foe of the Amazonians and Wonder Woman decides to go out and stop him. They kinda have this cheeky "Oh, Wonder Woman was here at this famous event" thing going on that's meh. Later in the film, other warriors join her and Chris Pine and his soldiers in a battle against Ares. Reminds me a lot of Captain America with the soldiers they freed.
There's also a really cool opening scene in Themyscira that reminded me of the opening to Man of Steel. It shows when Ares attacked a long time ago and it establishes that conflict makes him stronger.
A sequel to Suicide Squad is being considered. If SS does well, they may make a Birds of Prey movie.