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Based on the advanced technology of the 31st century, Kang and his variants have become exceedingly adept at manipulating and controlling time. This implies that he will always be vigilant towards any abnormal impact on the timeline, while also paying particular attention to individuals other than himself who may discover the principles of time travel, including Tony Stark.
In his final adventure within the MCU, Tony Stark invented a device allowing the Avengers to time travel, returning to the past to collect the 6 Infinity Stones and undo Thanos's deadly snap. Although Kang the Conqueror had not yet appeared at this time, intervening in the flow of time, it's highly likely Iron Man had clashed with the new villain of the MCU. This becomes even more convincing as the Iron Man needed to traverse the quantum realm - where Kang has been imprisoned for many years.
Iron Man may have encountered Kang upon discovering the time travel mechanism in Avengers: Endgame.
Hero among heroes, Kang deeply respects, even admires Tony for his ability to invent unimaginable innovations within the technological limitations of the 21st century. This is why He Who Remains preserved Iron Man's armor, as a gesture of admiration for Tony's enduring invention. This could even serve as inspiration for him to craft armor for himself, enabling him to confront even the mightiest superheroes, as somewhat depicted in Ant-Man & the Wasp: Quantumania.
From the analyses above, it can be affirmed that in some reality, Iron Man had encountered Kang, or more precisely Mr. Gryphon, and sold Stark Tower to him. However, this reality has clearly been erased by the TVA and cast into The Void long before Loki arrived. It should be noted that in the main MCU universe, Earth-616, Tony also sold the Avengers Tower in Spider-Man: Homecoming. However, the new owner's identity remains a mystery to this day, leaving open the possibility that it could be another variant of Kang the Conqueror.
Iron Man once confronted Kang in Secret Wars.
While Robert Downey Jr.'s return to the MCU remains only at the rumor stage and has not been officially confirmed by Marvel Studios, it's not out of the realm of possibility that the blockbuster Avengers: Secret Wars will bring back many old characters to deliver the most spectacular conclusion to the multiverse storyline. This means that the diverse cast of X-Men from 20th Century Fox, or Sony's Spider-Man versions, and even the departed Avengers like Tony Stark, Steve Rogers, and Natasha Romanoff, all have the opportunity to return to the MCU.
However, even if Avengers: Secret Wars doesn't feature Robert Downey Jr.'s return in the current MCU timeline, Kang the Conqueror's time-traveling abilities could still recreate the battle between him and Iron Man in the past. This would create a new timeline parallel to Earth-616, with fiery confrontations between Kang and the early generation of superheroes. This aligns perfectly with Ant-Man & the Wasp: Quantumania, where Kang reveals that he has fought and even killed numerous members of the Avengers.
