This is an allusion to the Argonauts As well as this image by Oliver Coipel where Tony demonstrates his ability to control several armors at once using tech similar to the NTU-Telepresence armor.
You can see in this still shot he is wearing what I believe is a Telepresence headset.
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Elsewhere in that same trailer, we see a flying Iron Man suit that Tony jumps into .
The back of the suit is open, and he leaps into it, then takes over.
This suggests that these suits may be remote controlled, so it's likely that most of them are empty in that image.
It's unlikely that if there are pilots in the suits that they would be Avengers, as Kevin Feige, Marvel Studios President stated in an interview : Journalist:
After cell phones came out horror directors had to come up with elaborate ways to explain why people wouldn’t call someone on a cell phone for help, now that all The Avengers know each other do you have to come up with excuses for why Tony Stark wouldn’t reach out when he needs a hand?
Feige:
It’s a good question, and it’s sort of half and half.
I am betting that like the comics you don’t have to keep – if you are reading a standalone
“Iron Man” comic, they don’t spend every page explaining where every other Marvel hero is.
The audience kind of accepts that there are times when they’re on their own and there are times when they are together.
I’m betting that movie audiences will feel the same way.
That being said, there is a little bit of lip service here and there to that.
There is also just the very nature of Tony wants to, once he barely survives that house attack
you saw today, and even you saw it in the message he left for Pepper
, he’s basically saying “I’m going off the grid to try to figure something out.”
It's currently unknown who is controlling them remotely (Tony, JARVIS, a villain, etc.), as the film is not yet released.
It's likely that Tony is doing so, as in a previous trailer (Trailer 1 at 0:27)
we see him wearing a device on his head and remotely guiding components of a new Iron Man armor onto himself.
In addition, it's been discussed in interviews that the movie will adapt the Extremis storyline.
In that storyline, Tony gets some augmentations to himself, which allows him to remotely guide and control Iron Man suits.
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Spoiler:
They are remotely controlled by him: Operation "House Party" The movie came out last week in japan (4/26/2013)
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Armors in the film were mark 25 striker mark 33 silver centurion mark 38 igor mark42 mark 17 heartbreaker
mark
40 shotgun mark 39 starboost mark 35 red snapper mark
37 hammerhead..
These are the armors Stark built in the film.
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The suits were all (almost all) unmanned, and controlled remotely by JARVIS as part of operation "House Party".
They are all the various prototype and production suits Tony had built.
During the battle in which they participated, Tony jumped from suit to suit, as needed, which is why I say "almost all" are unmanned.
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We've had an example of someone else wearing Iron Man Armour in War Machine, if a big enough threat makes it's self apparent
there is no reason Tony couldn't have a military unit suited up in a set of Iron Man suits.
About 1:50 in this trailer
we see what looks like people being measured for suits?
That could hint at an army of Iron Men?
Although the conversation between Tony and Rhodes: "We do need backup" "
That's Your department" And
"There's my boys" Imply that it might not be military, and might be as other have suggested remotely controlled, or AI controlled Iron Men.
There is precedent for this, the suits that Vanko puts together in Iron Man 2 are remotely controlled.
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It looks like there are about fifty Iron Men in the new Iron Man Movie:  Iron Man 3 .  Who are all these Iron Men? Is Pepper Potts one of them? Or is it all The Avengers, but wearing Iron Man costumes?  Here's a snapshot from the  international trailer :
Who are all the other ‘Iron Men’ in the Iron Man 3 trailer?
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<marvel-cinematic-universe><iron-man><marvel><iron-man-3>
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They are all various prototype and production suits Tony had built. During the battle in which they participated, Tony jumped from suit to suit, as needed, so "almost all" may be unmanned. I tis also unlikely that if there are pilots in the suits that they would be Avengers. The suits Tony had built are mostly all unmanned and controlled remotely by JARVIS.
The suits Tony had built are mostly all unmanned and controlled remotely by JARVIS.