This is my opinion on who will appear in Batman v Superman.Keep in mind that this is just a theory.Let's start.
It's called Batman v Superman I don't need to explain.
Again its called Batman v Superman.
3. Wonder Woman
We saw Wonder Woman in the trailers multiple times.We saw her like Diana Prince and we saw her defending Batman from Doomsday.So it's not a big secret that Wonder Woman is on this list.
I'm not a 100% sure that Aquaman will appear in Batman v Superman.But if he appears he will appear with Wonder Woman or later.There is an action figure of Aquaman in the DC Headquarters (I'm not sure if its called like that I am just guessing) so he may appear in the movie.I wouldn't like Aquaman to appear in the movie because 4 heroes(characters) is enough which brings me to my last one and the best one.
This would be amaaaaaaaazingg!!!!!!!!!!!!!! Victor Stone a.k.a Cyborg would be the best part of this movie.In the new trailer we saw Batman in his The Knightmare Batman costume snapping necks of Superman's army or Superman's soldiers.We saw parademons flying by and that can only mean one thing DARKSEID IS COMING! Yep that's true now I don't think that Darkseid will appear in Batman v Superman I think that parademons will attack Victor and the only way to save him is that his father Silas outfits him with experimental prosthetics of his own design. The equipment can not be worn inconspicuously, and Victor is horrified upon discovering that most of his body and part of his face have been replaced with metallic implants. Victor initially wants to die, but he eventually adjusts to the changes and learns to control his implants.And that's how Cyborg will appear in Batman v Superman.Check out the trailer.