Warning: This post contains spoilers for the plot of the Marvel Comic version of Civil War, which could also be true for the cinematic version, Captain America: Civil War, and in its aftermath in [The Avengers: Infinity War](tag:738027) Part I and II and also from Avengers: Age of Ultron
When [Captain America: Civil War](tag:994409) was first announced, I immediately had three questions that I'm sure most Marvel fans also had. Will Iron Man and company be in the film? (Yes!) Will Spider-Man make an appearance? (Not confirmed, but yes!) And finally, will the Civil War end with Steve Rogers being (presumably) assassinated?
Considering we have a Joss Whedon inspired Marvel universe, where our hearts are too often ripped out just to be put back, (Agent Phil Coulson, anyone?) I would think that they make Steve bite the bullet in the film.
In the comics, Steve's attempted murder was orchestrated by the Red Skull, who in Captain America: The First Avenger, disappeared in the same Tesseract vortex as Loki did in Thor. With Loki alive in well, where has the Red Skull been? I'd say working on revenge towards Captain America, which could also tie in with Thanos, much like has been the theme of the past few films.
If they set up the resolution between Rogers and the Winter Soldier (Bucky Barnes) early enough in the film, it wouldn't be too far fetched for Infinity War Part I to begin with Barnes picking up the mantle, much like the comics.
However, I, much like every other fan of the first two Avengers films, would be pretty disappointing not to see the original six Avengers square off against Thanos. While I am a big fan of the new lineup that Steve debuts at the end of Ultron, with Steve, Black Widow, War Machine, Falcon, Scarlet Witch, and Vision, it lacks the WOOOPAAAA of the original roster.
So what better way to get that element back than to bring Steve back, right in the middle of a war with the Mad Titan? Hearing the "Assemble" battle call from Steve would be exactly what the scrambling Avengers would need to gather for one last battle, and send even more people in line to buy movie tickets.
While most likely the film would follow the comic path and leave Bucky as Captain America and Steve Rogers as just Steve Rogers: Super Soldier, a film with two different Captains would leave even Thanos shaking in his size 35 boots.