Thinking he will come to the fore to take the mantel from John Walker
The whole series has been designed so that us, the viewers, will accept Anthony Mackie as the new Captain America when he shows up in subsequent movies because we all know how it will end. But frankly, I don't think it's needed or wanted. As a character, he's already a superhero in his own right and he seems very comfortable and happy with his current superhero persona.
Why is there a desperate need to have a replacement Captain America? Legacies should be respected and allowed to pass. And new symbols come out all the time, what did people do before Captain America existed?