There are a couple of interesting points of note in this scene. The first is that black hand, which appears to belong to War Machine. We know that Bucky and Iron Man are going to face-off, but is this a tease of a fight between Bucky and Rhodey, with Cap doing his best to calm the situation down? The other thing to spot is that Bucky has some straps around his chest, which would indicate he's wearing a backpack of sorts. Combined with the mountain shot, maybe 2015 was just a really extreme gap year for him between Captain America movies. Seriously though, chances are if he's wearing something strapped to his back, there's got to be a significance to it. A weapon, maybe? Or something less destructive, but equally important?