If you want to know a sure-fire way to open a can of worms, just include time travel in a movie. While Avengers: Endgame did a pretty good job of explaining its time travel rules and mechanics, as well as wrapping up character arcs and the larger Infinity Saga, there are still some loose ends, particularly those regarding Captain America. The end of the film sees Chris Evans’ Steve Rogers go back in time and stay there to reunite with Peggy Carter.
This has left many fans with some unanswered questions, like whether or not that is an alternate timeline or the main timeline or what. It’s a debate that many are still having months after the film’s release, and Avengers: Endgame’s writers Christopher Markus and Stephen McFeely love to see it. Addressing the ongoing fan debate over Captain America’s ending, the duo said:
Stephen McFeely: Oh, it’s great!
Christopher Markus: Yeah, that’s fine. Those are unsatisfied questions. Those are intrigued questions. I’m delighted at people still chewing over this thing. You know, if it’s, 'That’s stupid and I don’t like it and I’m talking about it because it was dumb,' that’s one thing. But if it’s, 'I honestly don’t know, and it’s kind of cool to think about,' that’s great.
You might think that the Avengers: Endgame scribes would be frustrated that people are still debating their ending for Captain America, but in reality they are all for it. The duo loves seeing the fans continue to discuss and theorize about Captain America’s time travel adventure and the wider implications of his choice in the film.
As they told Vanity Fair, Christopher Markus and Stephen McFeely love the debate because the fans are diving into intriguing unsatisfied questions. The debate is a reflection of how much the fans love and care about the film and the characters and the theorizing about Captain America’s ending is an example of that engagement.
The writers might not be as thrilled if people were still debating something in Avengers: Endgame because they didn’t like it or thought it was stupid, that is not the kind of conversation they want for their movie. Sure, some fans might still see plot holes or have issues with some things in Avengers: Endgame, but that has not been prevailing narrative around the film or Captain America’s story.
The fact that fans are still discussing this is testament to how much people are still thinking about Avengers: Endgame. And what’s fascinating is that the debate continues as fans come up with their own answers, despite the writers actually offering their own opinions on how things actually worked.
Christopher Markus has previously said that Captain America did not create a new timeline when he left a knowing Bucky Barnes and Sam Wilson to go return the Infinity Stones. It was his belief that Steve went back and just lived out his life in the main timeline, not an alternate one. Markus and McFeely have also stated that they believe Steve Rogers was always Peggy Carter’s unseen husband and the father of her children.
So that’s the closest thing to a canon answer as you can get, but the Avengers: Endgame writers don’t seem to have any problem with fans coming up with their own headcanon for Steve Rogers’ final mission.