Before continue you need to know that this article can contain spoilers.
According to some internet's sources we will see Captain America, Winter Soldier, Falcon, Black Panther, Black Widow, Iron Man, and Hawkeye.
We will see also Scarlet Witch, The Vision, War Machine, and Ant-Man(to see him take on the Giant-Man form in a battle.)
Actually there is no more information about Spider-Man but he will probably appear.
But..wait..What about Quicksilver? We hope he won't dead.
As to villains we will see Baron Zemo and Crossbones. Crossbones will supposedly cause the accident with a lot of death and destruction causing the government to step in and put out the Superhero Registration Act.
The teams are supposed to be :
Cap, Black Widow, Hawkeye, and Falcon vs Iron Man, War Machine, The Vision, and Ant-Man, with the Scarlet Witch and Black Panther somewhere in the mix.
Falcon will have new costume with red and grey colours and Crossbones will have his mask.
After all this I have some questions:
What about Spider-Man, Quicksilver and...Doctor Strange? Will we see them with Ulysses Klaw?
However, this can change so we have to wait an official confirmation.