Kudos to Jack Stero, from Moviepilot, for picking up on this. Check out his article to see how the new shield will function, basically it seems to be magnetized.
Like many people, I too assumed that the shot of Cap’s shield broken in half from the first trailer was either a dream sequence or some kind of Scarlet Witch vision. This still may be the case, and it’s just assumed that Cap has had some upgrades since we last saw him in The Winter Soldier. But hey, that’s no fun. What is fun is to speculate how this upgrade may occur in Age of Ultron.
Many people have speculated that this city we see The Avengers’ quinjet fly over in the second and third trailer is in fact Wakanda, and what other reason would The Avengers have to go there other than to stock up on some vibranium. I mean, they’re not exactly on a first name basis with T’Challa just yet. Which could cause some conflict…
We probably won’t see that in this movie, though, having The Avengers “borrow” a little vibranium is probably what causes Black Panther to confront our heroes in 2016’s Civil War.