A plot where Iron Man ages like Old Man Logan or Old Man Hawkeye would never work, no matter how many different universes future Marvel Cinematic Universe movies might explore. Since Tony Stark's demise in Avengers: Endgame, there has been a lot of chatter about how and when Iron Man would return to the big screen. The next individual to wear the Iron Man armoured suit will need to have a distinct appearance from the Tony Stark they have seen age over time.
Since Iron Man (2008), which served as the MCU's official debut, Tony Stark's journey has been one of gradually letting go of his infamously enormous ego and selfishness. He was essentially a self-centered guns dealer prior to first putting the suit together. The finale of 2012's The Avengers saw him finally understand the meaning of selfless heroism, riding a missile through a wormhole and almost losing his life to destroy Loki's forces invading New York City, after years of using his technology for the sake of the world over his own. From there, the movies leading up to Endgame painstakingly developed Tony Stark into a hero who could genuinely willingly sacrifice his own life in order to save the lives of others.
Death hasn't stopped MCU characters from making comebacks, but watching Robert Downey Jr. play Iron Man again as an older, presumably wiser version of the character would only lessen the significance of what the character took so long to learn. Tony Stark's journey was always a one-way path to a definite goal of choosing true selflessness from the comically inflated narcissist he began as. This version of Tony Stark would not have made the ultimate sacrifice that defined his character arc if he were to return in a later MCU plot.
Why Tony Stark's Early Death Was Always Intended
Furthermore, Tony Stark's characteristically narcissistic recklessness only serves to highlight how out of character his continued youth is. It's critical to keep in mind that this is the same individual who rashly disclosed his true identity on a global scale, purposefully mocked adversaries with his home location, and (in his own words about the since-deceased Loki) had a "monument constructed to the sky with his name plastered" on it. The morality of Tony Stark's decisions would be devalued by his long-term existence, which would also lessen the impact of the brazenness that has always made him stand out. Protecting others was his sole focus during his time in the MCU. If anyone was willing to give their life for the greater good, it was always going to be Iron Man—even more so than Captain America.
It makes sense that a plot about an older Tony Stark may appeal to fans given the critical and financial success of Marvel character films like Logan that explore more mature versions of cherished characters. On the other side, this might present a beneficial chance for an established hero to give over the baton, creating an intriguing opportunity for a fresh face to don the Iron Man armour. Since there is never a shortage of applicants inside the MCU who have proven more than worthy of the challenge, Tony once said, "If you're nothing without the suit then you shouldn't have it."