With Phase Four of the Marvel Cinematic Universe approaching, it's pretty clear that major changes are in the offing. A main aspect of this change likely involves a passing of the guard, with heroes like Chris Evans' Captain America and Robert Downey Jr.'s Tony Stark/Iron Man among those expected to ride off into the sunset.
While Cap's potential demise is something many fans are already debating, the possibility of Stark's story coming to some sort of conclusion is the potentially bigger development. After all, his solo story kicked off Marvel Studios' initial vision for a movie universe in 2008, laying the groundwork for making Iron Man the anchor of the MCU. Whether it's via retirement or assome fans suspect, death, Stark's absence will leave a huge hole in the fabric of the MCU. However, there's already a potential replacement waiting in the wings, one who's just as intelligent, albeit with a bit more sinister element to him: Doctor Doom.
21st Century Fox has Legion creator Noah Hawley writing his solo movie presently, although plans could shift due to the seemingly imminent acquisition by Disney. And with Phase Four not starting until 2019, when the Spider Man: Homecoming sequel will kick it off after Avengers 4, Marvel would have time on its side to engineer such a bold move.
While it would certainly be a headline-grabbing development, however, there are genuinely solid story-based reasons why Doom is the perfect man to take control of Iron Man's armor in the the MCU.