In the comic books, Ultron was created by Hank Pym and ended up becoming one of the Marvel Universe's greatest villains. No matter how many times he was defeated, the sinister android found a way to return and even earned the ultimate victory in the post-apocalyptic "Age of Ultron" timeline.
Ultron even served as a cosmic baddie for a time, matching wits with the Guardians of the Galaxy.
Taking all of that into account, it's hard not to feel like he might have been wasted in the MCU. Despite being a fantastic villain in 2015's Avengers: Age of Ultron, making him a one-and-done baddie closes the door on all manner of storytelling opportunities. Then again, we never did see The Vision kill his "father."
Now, with Vision Quest and Armor Wars on the horizon, theories have been running rampant for a while that Ultron could return in the not-too-distant future.
According to information obtained by moderators on r/MarvelStudiosSpoilers, James Spader is indeed set to reprise the role of Ultron in Marvel Studios' Armor Wars movie.
Original plans called for that to be a Disney+ TV series, with the decision later made that it was a big enough story for theaters. Ultron's return sounds about right then and it's incredibly exciting to think about the many ways he could factor into this story.
Ultron is fresh in all of our minds following the events of What If...? as he was a threat to the entire Multiverse there. After successfully inhabiting what would become The Vision's body in the MCU, he acquired the Infinity Stones and became aware of The Watcher's existence. Unleashing war on the Multiverse, he was eventually stopped by Captain Carter and her team.
Only time will tell whether Spader really is coming back as Ultron, but we're keeping everything crossed it eventually happens.