Quicksilver and Scarlet Witch Are Protesters
This early shot from the trailer might look like an establishing shot of civil unrest, but it does more than establish a tone. It's also our first glimpse of Quicksilver (Aaron Taylor-Johnson) and Scarlet Witch (Elizabeth Olsen), presumably from before they had powers. They look pissed off, and since they're not alone, it's probably for a good reason that will probably pay off in the film.
Is This Robot The Vision?
Ultron destroys what appears at first glance to be a suit of Iron Man armor, but upon closer inspection appears to have no room to put a human inside. Since we know The Vision appears in Avengers: Age of Ultron, it may stand to reason that this was an early robot body for Tony Stark's A.I. butler, J.A.R.V.I.S., necessitating an upgrade later in the film to face off against Ultron.
Someone Is Playing Doctor
Close-ups of scary-looking medical tools usually aren't used to portray a routine physical. Someone is getting operated on in Age of Ultron, and you can get a hazy shot of whom in the background of this shot. Is this Quicksilver and/or Scarlet Witch? The Hulk? Don't rule that second theory out. We'll get to that...
Quicksilver and Scarlet Witch Are Working with Ultron
Quicksilver and Scarlet Witch appear behind Ultron in this ominous shot from the trailer, and he seems to have no problem with them being there. Could their anger at an unknown injustice drive them to work with the enemy of all mankind?
Ultron Has An Army
That's a lot of Ultrons. It looks like The Avengers will have another army of faceless bad guys to beat up without losing audience sympathy.
Nick Fury is Back
Well, that didn't take long. It looks like the Ultron fiasco was enough to bring Nick Fury out of retirement pretty quickly after the events of Captain America: The Winter Soldier, but will this just be a cameo, or will he have something more to contribute to the team?
Hulkbuster Armor is Worn Over Regular Iron Man Armor
This is a minor observation, but Tony Stark is clearly wearing his standard armor under the Hulkbuster armor in this shot from the Age of Ultron trailer. The larger Hulkbuster helmet goes on over his normal helmet. Clearly he needs all the help he can get to take down The Hulk. But we still don't know why The Hulk is going berserk... or do we?
This Robot Means Something to Tony Stark
Although the helmet damage is different, the markings on this robot certainly look the same as the markings on the robot that Ultron destroyed at the beginning of the trailer. This lends a bit more credence to the theory that the robot was The Vision. Why else would Stark look at it so guiltily?
Andy Serkis is Playing... Someone
It's official: Andy Serkis is definitely in Avengers: Age of Ultron, and not just as a motion-capture character. We still know nothing about who he is in the movie except that he has a very distinctive beard. Anyone got any ideas?
Quicksilver Turns on Ultron
Scarlet Witch probably does too, if her pissed off scream earlier in the trailer is any indication. But here we definitely see Quicksilver using his super-speed to fight a robot on a train alongside Captain America. Third-act reversal, anybody?
Mysterious Ballerinas of Mystery
Right in the middle of the crescendo moment in Avengers: Age of Ultron trailer, there is one shot of ballerinas rehearsing. This may just be a Joss Whedon gag - he did a whole episode of "Angel" about ballet, after all - but then again it could also mean that the film will show us Black Widow's origin. She was supposedly a ballerina in the USSR before she became an assassin.
Hulk & Hawkeye Team Up... Or Do They?
An early shot of Bruce Banner running through the woods - and not looking so hot - matches almost perfectly with a later shot of Hawkeye running through a very similar looking set of trees. Does this mean they team up? Or does this mean Hawkeye had to save Bruce Banner, perhaps from that doctor we saw earlier in the trailer? Either way, it looks like they're on some kind of adventure together. Does the reason Bruce Banner is on the run have anything to do with the shot of the doctor earlier in the movie? Does it have anything to do with why he goes on a rampage later in the movie?
Hulk and Black Widow Are Growing Close
This one brief shot from the Avengers: Age of Ultron trailer shows The Hulk reaching out to The Black Widow, and not in anger. That's a pretty big counterpoint to their fight (well, chase) in the previous film. Have they gotten closer between films? Could this even be a hint of romance between Avengers?
Ultron May Be Coated in Vibranium
Since Marvel Studios doesn't own the rights to adamantium - the fictional, indestructible metal that coats Wolverine's claws and, in the comics, Ultron's body - it's very likely that this early shot of Ultron shows the villain covering himself with vibranium. That's the same stuff Captain America's shield is made out of, which would explain how it could possibly break, as we see in one of the last shots of the Avengers: Age of Ultron trailer.
[UPDATE: And if Andy Serkis really is playing the vibranium-laden villain Ulysses Klaw, this theory makes even more sense.]