As one of the main characters on The Walking Dead, he has amassed a huge fan base, and certainly has experience with both a major franchise and the action-adventure genre.
Reedus is, of course, still a big part of The Walking Dead — unlike Rooker, whose character was killed off in the third season of the show.
Reedus would certainly be a fan favorite as an addition to the MCU.
And, of course, there are still hundreds of Marvel characters who could one day make it into the massive expanded Marvel universe.