Chris Evans' Captain America is enjoying a quiet retirement in the Steve Rogers, who kindly offered to take the Infinity Stones back to their rightful homes. Instead of coming straight home, however, Cap decided to reunite with his one true love, Peggy Carter. Living a full and happy life with the SHIELD legend, an older Steve finds Bucky and Sam Wilson in 2023 and es his patriotic shield onto The Falcon.
On the opposite side of the Marvel and DC divide, Frank Miller's 1986 The Dark Knight Returns is a seminal release in Batman's lengthy canon, set following a period of peacefully dull retirement for Bruce Wayne. As Gotham City descends into darkness once again, Batman returns to the crime-fighting game to take out the Mutant Gang, Two-Face and Joker. The Batman's return irks the authorities, leading to the legendary confrontation between the Dark Knight and Superman.
At present, there are no plans for Chris Evans to reprise his role as Captain America, but the longer the MCU continues, the more likely a return for Steve Rogers becomes, and The Dark Knight Returns would be a good place to start. Rogers might've ed his shield onto Falcon, but the OG Captain America is still alive in the MCU, and could live for decades thanks to the super serum coursing through his veins. Even as an old man, he could probably still run rings around most criminals. In The Dark Knight Returns, Bruce was bored of retirement and compelled to continue his vigilantism due to a sense of duty and the decaying morality of Gotham City. After Peggy es away, Steve could find himself at a loose end. It's well documented that one of Steve's biggest virtues (or, indeed, flaws) is his selfless dedication to fighting the good fight, and even as an old man, Steve Rogers would never deny the call to make a positive difference.
Thematically, Captain America's return could closely parallel Batman's comeback in The Dark Knight Returns. Bruce squeezes back into his Batsuit when evil begins to override good in Gotham City. The authorities and other heroes are struggling against the Mutant Gang, leaving the good citizens of Gotham desperately seeking a ray of hope, and Batman's return provides that, even if the U.S. government disagree. Captain America has always been as much a symbolic figure as he is a superhero, and if the MCU finds itself in a similarly grim period, the very first Captain America emerging from the shadows would lift the entire world, copying Batman by proving that true heroes are still willing to fight.
One potential entry point for an older, grizzled Steve Rogers could be a future season of U.S. Agent to prove his supposed "successor" isn't fit to lace the real Captain America's boots. After all, only one man who can claim to have "America's ass."
As a political creation, U.S. Agent would naturally hold the of his country's government, thereby aligning Steve Rogers against the White House, much like Bruce Wayne in The Dark Knight Returns. A "Steve Rogers vs. The Man" storyline would work perfectly in the MCU, playing off Cap's rebellious Sokovia Accords phase. The events of Captain America: Civil War were somewhat forgotten in the aftermath of Thanos, but a Dark Knight Returns style story could finally finish off that MCU arc.
