In a recent interview with The Huffington Post, the film's directors, Joe and Anthony Russo, revealed that Cap's decision to leave his shield behind after defeating Iron Man (Robert Downey Jr.) at the end of Civil War will have a lasting impact on the Marvel cinematic universe.
"I think him dropping that shield is him letting go of that identity," Joe said. "[It’s] him admitting that certainly the identity of Captain America was in conflict with the very personal choice that he was making."
However, this doesn't mean that Steve Rogers won't still be defending the world, he may just be doing it with a different alter ego. Of course, based on the comic books, this new identity would likely be that of the Nomad — the superhero Steve turns into after becoming disenchanted with the U.S. government.