Chris Evans as Captain America in Avengers: Infinity War. Image courtesy of Disney.
How Captain America could die in Avengers 4
Captain America dies to save Bucky as well as the other heroes who have been dusted by Thanos
We all know that Steve Rogers has had to see Bucky Barnes die in front of him twice now and that he wasn’t able to do anything to stop it. Assuming that the remaining Avengers are trying to find a way to get back those they lost, it wouldn’t be surprising if Steve Rogers sacrifices himself to save Bucky, Falcon, and other people he cares about. This is very in line with his character and would be a tragic but heroic ending for Captain America.
Captain America “dies” to go back in time and live with Peggy, or live a life with her in the afterlife
This one is very much in the fan-theory category. According to some fans, they want to see Steve Rogers and Peggy reunite. Since time travel looks like it is going to play a role in Avengers 4, Steve, as we know him, could die in the sense that he remains in the past and lives a different life with Peggy. The film could also kill Steve and have him reunite with Peggy in some sort of afterlife, mirroring the scene in Avengers: Age of Ultron when Scarlet Witch messes with the Avengers’ minds where the two meet to dance.
Captain America dies to give the rest of the Avengers a chance to save the world
There is some comic book precedence to the death of Captain America. In the comic run of Civil War, Steve Rogers does die. They could follow through on this idea and have him die in Avengers 4. A leaked image of Cap’s possible Avengers 4 suit could add credibility to this theory as it is similar to the suit Steve wears when he dies in the comics. It would make sense if Steve Rogers dies in some attempt to allow the rest of the Avengers the chance to defeat Thanos and save the world.