Charles Murphy, a trusted source recently revealed that Doctor Doom is going to be the main villain in the next Black Panther film. Doctor Doom who belonged to fox studios until the recent merger will be making his first appearance in the Marvel Cinematic Universe. Murphy described the rumours about a villian and said that he is, "expanding his empire, conquering parts of Africa and, ultimately, come into conflict with the nation of Wakanda and the Black Panther.”
Murphy stressed that for now these are mostly just rumours and not guaranteed. However Kevin Feige's approach to the Marvel Cinematic Universe suggests that this probably true.
Doom last appeared in Fox's rendition of the Fantastic Four films. However if he appears in Black Panther 2 it will be the first appearance of a Fox studios character in a Marvel film outside of Spider-Man. And will act as a way to integrate other characters into the larger cinematic universe.
Until now Namor, the sub Mariner rumoured to be the villain for Black Panther 2. Recent news suggests otherwise. Only time will tell what really happens with the fate of Wakanda and its king.