Also, its not as if some groundwork for their introduction hasn't been done already. It's explicitly stated in Captain America: The First Avenger that Cap's shield is made out of vibranium, a metal found almost exclusively in Wakanda, the African nation that Black Panther rules over. Also, the Kree alien race (aka the race which Ronan from Guardians of the Galaxy belongs to) are the ones that inadvertently end up giving US Air Force Officer Carol Danvers powers and turning her into Captain Marvel (or Ms Marvel as she was originally called). Marvel still have two more unfilled slots for 2017 on their recently revealed timetable, flanking Guardians of the Galaxy 2 's July 28 spot. I wouldn't be surprised if either Captain Marvel or Black Panther were to take the first space on May 5. I've previously guesstimated that the recently announced Inhumans movie would take the latter November 3 spot, but giving it to the remainder of the two would actually make a bit more sense.