There’s a major rumor going around that may lead to some major SPOILERS for Civil War, but if true it’s very faithful to the original comic storyline.
According to The Hashtag Show (via Latino Review) the movie will end just as the epilogue of the Civil War comic did. Now this is a spoiler, but as the comic has been out for a decade now, it’s not a major thing to say that Captain America dies at the end of that storyline. That’s why everyone has always speculated that Bucky would take up the shield in the movies someday.
Since Civil War is by far Marvel’s highest selling trade paperback, even ten years after the comic event, this isn’t something that would be shocking to most people. In fact, I’d say most people are expecting this to happen in the movie.
What’s surprising is the Hashtag Show says there are three different endings filmed. One has Bucky taking up the shield, the other has Sam Wilson doing so (to match the current comics), and the other has Sharon Carter becoming the new Captain America. That’d definitely be a change from the comics if they end up doing that angle.
For now this is a rumor, but based on the subject matter and the expectations of fans it wouldn’t be shocking if Marvel did this.