Will Ultron be returning to the Marvel Cinematic Universe? A new Marvel theory predicts that it could (and might) happen in the new Marvel Cinematic Multiverse that Loki has unleashed. The theory actually pulls different breadcrumbs from the upcoming Marvel's What If...? series on Disney+ together, and predicts that the anthology series will actually have a larger story arc featuring Ultron. Various pieces of What If...? marketing and promotional materials may hint that variant versions of Marvel heroes will be brought together as a team by The Watcher, to stop none other than Ultron from conquering the Multiverse.
Guardians of the Multiverse
The characters featured in What If...? have been well-hyped and teased by now. Peggy Carter (Hayley Atwell) will become a Super-Soldier; Thor (Chris Hemsworth) is a party boy; Doctor Strange (Benedict Cumberbatch) takes a darker path; T'Challa (Chadwick Boseman) becomes Star-Lord and leaves Earth; Black Widow (Scarlett Johansson) never leaves the Red Room; Erik Killmonger (Michael B. Jordan) conquers Wakanda with Tony Stark's help, and Gamora (Zoe Saldana) becomes the Mad Titan instead of Thanos.
All of the aforementioned characters appeared together as a team on a piece of What If...? marketing material that leaked earlier this year. That promo image dubbed this team the "Guardians of the Multiverse," which led fans to an obvious question: whom or what are they guarding against?
What If....? Villain Is Ultron
The final wave of What If...? marketing has given fans a much better look at what the series will be, and if you look at the footage with the "Guardians of the Multiverse" concept in mind, you may begin to notice a larger story arc at play - and Ultron at the center of it.
That idea is supported by two key themes within the What If...? trailer footage: the various members of the "Guardians of the Multiverse" clearly meeting one another and fighting together, and scenes of an entire armada of Ultron's drones all launching and attack various heroes.
It's Happened In The Comics
Ultron nearly overran Earth in the main MCU timeline during Avengers: Age of Ultron; Marvel Comics has already set precedence for Ultron being a major cosmic threat as well (see: "Annihilation Conquest"). Ultron also battled none other than Kang the Conqueror in one story arc, in which Kang tried to conqueror a reality where Ultron ruled. With Loki tying the MCU version of Kang to this Multiverse concept, Ultron is one enemy that could threaten Kang and his variants.
That's all to say: there are pretty deepcomic roots for bringing Ultron back as a threat to the entire Marvel Cinematic Multiverse in What If...?. Especially if there is a reality out there where the Avengers never successfully stopped the robotic villain from conquering Earth - or the galaxy.
Some theories go so far as to predict that the Marvel Zombies featured in What If..? will actually be used as a rival army to battle Ultron and his drones - as we saw in Marvel Comics' "Secret Wars" arc in 2015. It would be yet another Easter egg pull from the larger saga of the Marvel Comics multiverse, which fans would know and appreciate.