Like so many Marvel Studios movies, Avengers: Infinity War has shown improved visual effects with every new trailer or TV spot that's been released. In the latest versions, we've seen a vastly improved shot of Captain America, Black Panther and Co. from charging into the fight during the "Battle of Wakanda" sequence of the film. Marvel fans were left buzzing about Steve Rogers' new mechanical shields, while other Marvel fans immediately focused in on a different (albeit just as exciting) new detail:
That shot clearly calls back to Black Panther's post-credits scene, in which we see Bucky / The Winter Soldier awakened from cyro-sleep by Shuri. The scene ended with Shuri telling Bucky that there was much more to do - and they set off to do it.
Presumably, Shuri was outfitting Bucky with this new bionic arm, which looks slightly darker and has all kinds of gold-tinted markings running through it, in the spirit of Wakandan design aesthetic. It almost looks like an arm of the Golden Jaguar suit, re-fitted for Bucky.
With this new design comes the question of what new tech Shuri also included in the arm. If it's anything like Wakanda's other Vibranium tech (ex: the most recent Black Panther suits), then Bucky may be able to use the same "sheathing effect" to mask his arm as a normal sleeve, redirect energy, etc. In other words: Wakanda could give Bucky a pretty major upgrade.
However, arming The Winter Soldier with Wakandan tech may ultimately backfire, if the nation turns against T'Challa for harboring him. It's just one line of dominoes that Marvel has set up to fall in later MCU films like Black Panther 2.
Black Panther is now in theaters. It will be followed by Avengers: Infinity War on May 4th, Ant-Man and the Wasp on July 6th, Captain Marvel on March 8, 2019, the fourth Avengers movie on May 3, 2019, the sequel to Spider-Man: Homecoming on July 5, 2019, and Guardians of the Galaxy Vol. 3 in 2020.