One of the big questions leading into Avengers: Infinity War is what the ultimate fate of Captain America will be. There are numerous theories about what could ultimately happen to the character played by Chris Evans, as well as the title which Steve Rogers holds. One popular theory is that Cap's friend Bucky Barnes, aka the Winter Soldier, could take on the mantle, but Infinity War writer Christopher Markus hopes that isn't what happens. He thinks the Winter Solider is a perfectly great character on his own and doesn't need to become Captain America. According to Markus...
I will say, just on a fan level, I think Winter Soldier's so awesome that I'm always like, why are you wasting Winter Soldier and putting him in like Captain America outfit? You had two heroes now you got one.
Chris Evans has somewhere between four days and one year left to play Captain America, as we know his contract expires following Avengers 4. This leads to an expectation that he'll survive Avengers: Infinity War though that's far from 100% clear. Regardless, once Evans is done, Marvel will need to make some decisions regarding the future of the character. One popular theory is that the movies will do what the comics have done in the past, and bring in another MCU character to become the new Captain America. The two top candidates for the job have been Anthony Mackie's Falcon and Sebastian Stan's Winter Soldier, as they have an association with the existing Cap, and both characters have become Captain America in the comics previously.
Christopher Markus, who brought the Winter Soldier into the MCU as the co-writer of Captain America: The Winter Soldier with Stephen McFeely told ScreenRant that, rather than seeing Bucky Barns become the new Captain America, he'd like to see the Winter Soldier move forward as a character himself. It's true that, if Bucky becomes the new Cap, you're down a hero, but that's only true if somebody else becomes the new Captain America. In fact, the only way to not turn two heroes into one hero is if the role of Steve Rogers simply gets recast, or if an entirely new character we haven't met before becomes the new Captain America, both of which would seem to be long-shot options.
It will certainly be interesting to see how Marvel handles the departure of some of its biggest stars. While Marvel Studios found their major success in adapting the crossover strategy of Marvel Comics, how comics handle replacement heroes simply won't work on the big screen.
We'll see the beginning of the end of the current Captain America, one way or another, when Avengers: Infinity War arrives Friday.