Out of the three Avengers movies we’ve seen so far, Avengers: Age of Ultron is easily the runt of the litter, not necessarily in terms of quality (though probably that, too), but definitely in terms of its relevance to the overarching stories of the MCU.
Yes, the film introduced a couple of important characters, and the battle in Sokovia would later serve as an excuse for the events of Captain America: Civil War, but the central conflict between Earth’s Mightiest Heroes and Ultron just doesn’t feel like as pivotal a moment in the franchise’s history as their clashes with Loki or Thanos. Perhaps a key difference is that unlike his fellow Avengers villains, Ultron’s presence is entirely confined to this one movie, but with the new Captain Marvel Prelude comic, some fans feel that Marvel could be prepping us for the character’s return.
This new series is said to be laying the groundwork for Carol Danvers’ entrance into the MCU, while also filling in the blanks on what Nick Fury and Maria Hill have been up to for these past few years. But in one recap scene, the comic takes us back to the events of the 2015 film, and shows one of Ultron’s drones crashing into the helicarrier, only to be stopped by Fury.
Since this section seemingly holds no purpose plot-wise, there’s been some speculation that the comic is attempting to ease Ultron back into the saga. And while this theory may seem unlikely at first glance, there’s some precedence to this in an Avengers: Infinity War prelude comic, which revisited that moment where Red Skull met his fate in Captain America: The First Avenger. Like Ultron, Red Skull was a character who had no presence in the series beyond his one, years-old movie, and yet there he was again, in Infinity War.
It therefore doesn’t seem entirely out of the question that the Avengers: Age of Ultron antagonist will be making an appearance in Avengers 4, especially if all these time travel predictions are on the right track, but we’ll find out for sure when the film hits theaters on May 3rd, 2019.