Avengers: Endgame ends with a true tearjerker of a final scene, as Steve Rogers vanishes into the Quantum Realm to return all the Infinity Stones…only for an elderly Cap to appear on a bench nearby. Old Man Steve reveals that he stayed in the past and lived a happy life married to Peggy Carter. It’s a perfect ending for the hero, but his appearance in the main timeline has caused fans a lot of headaches. Based on the established rules of time travel in the MCU, Steve getting hitched to Peggy should have created a different timeline.
The Russos attempted to clear this up by saying that, yes, Steve did create a new splintered timeline. However, he must have hopped back over to the prime universe to deliver his shield to Sam Wilson and explain to his friends what happened to him. Ok, so case closed then, right?
Well, no, actually, as writers Christopher Markus and Stephen McFeely believe that Steve didn’t create a new timeline but remained in the main one, saying he’s been in this world the whole time and we just didn’t know it. For instance, Peggy’s kids that are referenced in Captain America: The Winter Soldier? They’re actually Steve’s, according to the writers.
CBR caught up with Markus and McFeely and asked them about how their conflicting explanation for Cap’s ending squares with the Russo’s version. Markus said that it was open to interpretation and, while he prefers his and McFeely’s theory, he called it “a question with many answers.” As for why Cap wouldn’t have tried to change history for the better with his foreknowledge if he did stay in the main timeline, the writer added: “We don’t have to write that!”
It remains to be seen whether Cap, Peggy or even their (presumably) super-powered kids will feature again in the MCU to either prove or disprove the writers’ theory. Until then though, like Markus says, Cap’s ending in Avengers: Endgame has many explanations, so fans can chose to believe whichever one they want.