[CODICIL: This is my very FIRST article after all these years. I've been around since this much-gloried site and Realm of Galactus since 1988, when most of the comic book movies you know and love were only "a glint in the milkman's eye". A veteran of the flame wars of just about ALL comic book movies since then, I say this: If I have stepped over any line, or violated any posting rule, I accept any and all tongue-lashings and reprobation as well-deserved.]
Okay.
Time for a little speculation and observation here.
1. THREE Helicarriers, GREATLY up-gunned, are being manufactured in the trailer, and we see them as the helicarrier is being lifted from "drydock" [sic]. Number "42", number "65" (the follow-on of the Avengers film Helicarrier 64) and number "88". 88 seems MUCH larger than 42 (look at the expanded "belly" of 88). 65 seems larger as well judging from the parallax of the shot. There seems to be at least three classes of Helicarrier, each of differing "displacement"/maximum takeoff weight, as well as armament.
2. The Winter Soldier catches Cap's shield. Cap's shield is supposed to be created from Vibranium, which absorbs/deflects all energies (allowing him to use it as a "brake" for water entry [guys - the shield deflects the impact of the shield to the water, allowing his super-strengthened humerus to hold the shield extended as his body hits a water surface]). So, Winter Soldier's arm is made of Vibranium, as well. Does this open the door for a film about the only earthbound source of Vibranium ore - Waukanda???
3. Red Skull masquerading as the head of SHIELD portrayed by Robert Redford has some precedent, and that is Trevor Slattery playing a role as The Mandarin. Maskirovka, the Russian term for masquerade. Appearances are not always correct. Red Skull has already been shown as a master of disguise. And we do know that Arnim Zola, in WHATEVER form he appears, is involved, somehow. It is possible that Red Skull returned to Earth sometime in the 1945-1991 timeframe (he would have had to have embedded himself in some way prior to the fall of the Soviet Union to have credibility in the SHIELD hierarchy), and reconnected with the "remnant" (?) of Arnim Zola and both have worked, undercover, to use SHIELD for their OWN purposes.
4. Fury is SHIELD to the bone. He moves against the SHIELD hierarchy, and is targeted by The Winter Soldier. Crossbones is working with The Winter Soldier, and we can assume that Batroc the Leaper (the guy who pulls the sword on Cao in the elevator?) is working with "the Dark Side" of SHIELD as well. There may be a bit of a "civil war" afoot in the SHIELD command structure. Fury may very well be fighting to take control of SHIELD back from the forces that are trying to use it for their own purposes.
5. "Agents of SHIELD" has GOT to start referencing these events, to remain relevant in the MCU. In fact, Agents of SHIELD might very well be the main tool used by Marvel to start the foreshadowing of a fracture within SHIELD, and the team on "the short bus" might start picking up the first murmurings of such conflict within the organization. Skye has ALREADY hinted that she is working with other organizations that have penetrated SHIELD. Could Marvel Studios be setting the stage for Cap 2, already, in the Agents of SHIELD storyline?
6. Decisions by The Council during "The Avengers" as an extension of Hydra's strategies. The Council orders the destruction of New York as a response to the invasion by the Chithauri, commanded by Loki. Is the Council working on the advice of the Robert Redford character (Red Skull?) to take advantage of the opportunity of the alien invasion to complete the original mission of Hydra to destroy New York?
7. "Phase Two". Cap finds that SHIELD is creating "Hydra weapons" based upon the Tesseract, and that this tech is on the Helicarrier. Hydra penetration of SHIELD to complete their previous plans? Is this what Marvel is hinting at, setting up Cap 2?
8. Thanos tie-in. We know that The Purple Grinning Titan Bastard is not some single-line actor. Thanos is devious, and never leaves all his eggs in one basket. He wanted The Tesseract. Loki was ONE avenue to that goal. Is it not possible that The Red Skull, who was ported to somewhere else by The Tesseract, ended up before The Purple Death-Dater and worked a deal for a return to Earth? Perhaps to work behind the scenes to undermine the most credible defense that Earth had (SHIELD) to help forward the Chithauri Invasion?
9. Cap dons the original uniform. Cap supposedly steals the original uniform from the Smithsonian. Some think it is to remind the public who he is, and that he is fighting for America, not for one faction or another, PURE Cap. But is it not possible that he dons the uniform to be a psychic kick to the nuts to his best buddy, Bucky, who has been brainwashed and manipulated? Cap seems to not fully see WHO the Winter Soldier is for a while in the film, a face blurred by smoke, or under a mask, but you can bet that he begins to SUSPECT that this new Super Soldier is Bucky. Him stealing the uniform from the Smithsonian might very well be about him trying to get the "real Bucky" to emerge from the brainwashed "Winter Soldier".
10. Agents of SHIELD, again. You can bet that if there is foreshadowing of a SHIELD penetration by Hydra leading up to Cap 2, that there WILL be aftershocks throughout Agents of SHIELD. Even if things are patched up with Skye by that point, a reveal that Red Skull became the leader of SHIELD might very well open old wounds in the team and make several think that Skye might very well be working under DEEP cover. This distrust plays quite well into the idea that Skye might end up as Jessica Drew, who was always viewed with a bit of a skeptical eye by teammates in the Avengers and other groups.
Okay. All of this is pure speculation. However, to me, Marvel does NOTHING in this cinematic universe as a "stand-alone". We are seeing a LOT of foreshadowing in this trailer, and are given a LOT to think about.