Does Bucky Become Captain America?
Both Sam and Bucky Have Taken up the Mantle of Captain America in the Comics, Both in the Absence of Steve Rogers. .. . Sam Becoming Captain America Isn't...
Both Sam and Bucky have taken up the mantle of Captain America in the comics, both in the absence of Steve Rogers. ... Sam becoming Captain America isn't simply a matter of Sam being better suited morally than Bucky (who has a history of HYDRA-assigned assassinations as the Winter Soldier).
Does Bucky ever become Captain America?
Bucky made two things clear before taking up the mantle, though: he wanted S.H.I.E.L.D. to get the Winter Soldier programming out of his head, and also to be his own hero, answering to no one. Bucky then donned a new costume to become Captain America.
Why isn't Bucky the new Captain America?
That's probably why Steve chose to give the Captain America shield and title to Sam instead of Bucky. It wasn't because Steve believed Bucky's reputation and past made him unfit to hold the shield, but because he wanted to save his friend from the pressure of having to deal with being Captain America.