We have had 3 villains confirmed so far, Arnim Zola, Batroc and Crossbones. But who do you think is the main villain? Batroc and Crossbones are more followers then leaders in the comics. Zola has sometimes has been a follower and other times has been a leader.
So do think Zola is the main villain or do you think there is a mysterious villain controlling things from the shadows, like Red Skull or Baron Zemo?
Don't forget the
Winter Soldier! From the trailer, he apparently puts Fury in the hospital (I mean, he's only the subtitle...
).
I'd guess Zola is probably the one who built WS's arm, but I'll be mildly surprised if he turns out to be the Big Bad. Batroc is probably a mostly-unrelated Act 1 villain, and Grillo has said this is largely an origin for Crossbones.
From the trailer, given the elevator fight, Falcon and Cap being chased by quinjets, and Redford's monologing, I think the "main" villain is likely
SHIELD, or some subset thereof, led by Redford. This fits in with the theme of questioning what Cap's place is in the modern world. Whether or not Redford is
someone else in disguise, and whether they are working with or against Zola, I'm not going to make a claim one way or the other.
OTOH, given all the misdirection in the IM3 trailer, I suppose anything's possible. Marvel's gotten pretty good about making you think a movie is one thing, and then surprising you.