With rumors of Steve Rogers/Captain America returning to the Marvel Cinematic Universe, there are all sorts of theories about ways in which Tony Stark/Iron Man would return as well. The character died sacrificing himself to defeat Thanos and his army in Avengers: Endgame.
Furthermore, the announcement of Avengers: The Kang Theory Y Avengers: Secret Wars has sparked even more speculation about a possible return of some of the original Avengers, in one form or another. Marvel could make the decision to bring Tony Stark back, at least temporarily, in one final fight.
With time travel, multiverses, and artificial intelligences, there are plenty of ways for Tony Stark to return to the Marvel Cinematic Universe. With and without Robert Downey Jr playing the character again. These are all the possibilities.
A variant of Tony Stark from the multiverse
It seems the most plausible alternative. A variant of Tony Stark, from a parallel universe who travels or is brought to Earth-616 to help the Avengers. Following the events of Loki, Doctor Strange in the Multiverse of Madness, and Spider-Man: No Way Home, it fits perfectly into any storyline.
At the time it was rumored that Tom Cruise could appear as a variant of Stark, but in the end it turned out to be false. But he doesn’t have to be such a high-profile actor. He doesn’t have to be male, even.
Travels in the time
Avengers: Endgame opened the door to time travel. Later, the possibility was explored in Loki with the TVA and even in Ms Marvelwhen the main character seemingly traveled back decades and ensured his own existence.
The possibility of traveling to the past and bringing Tony Stark to the future is there. It would have to be an extremely large motive, justifying going into the past, before he died, and taking him into the future. A bigger threat than Thanos may be justification enough.
Tony Stark as an artificial intelligence
This possibility would be a plot arc brought directly from the comics of iron heart. Stark created an artificial intelligence version of himself in case his body stopped working. After the events of Civil War 2he was left in a coma and his AI was sent to Riri Williams to mentor the character.
Riri Williams will be introduced as a new character in the Marvel Cinematic Universe in Black Panther: Wakanda Foreverwhich opens in November 2022.
Iron Hammer, Kang’s Soldier
There is a version of Tony Stark who plays a soldier to Kang, who will play a pivotal role in phase 5 and 6 of the Marvel Cinematic Universe as the main villain. The theory is based on the story arc in the comics, in which the villain creates an army of Thors called thor corps. Among them was a Tony Stark capable of lifting Mjolnir.
This variant is known as iron hammer. Seeing an evil version of Tony Stark, even played by Robert Downey Jr, can make for a very interesting story, but, let’s be honest, it will probably never happen.