Killmonger had a brief but complete character journey in ‘Black Panther’, but Michael B. Jordan's comments regarding a potential return for the MCU villain risks ruining his original story. Jordan's expressed love for Killmonger as a character, but has been vague when asked about him returning to the MCU. While Jordan's fans would no doubt welcome the actor reprising the role down the road, it would undermine what ‘Black Panther’ did with the villain.
Erik Killmonger was the main antagonist in ‘Black Panther’. Cousin to King T'Challa (Chadwick Boseman), he successfully challenges him for the throne and assumes the powers of the "Black Panther." He's intent on avenging his father's death and honoring his legacy by using Wakanda's advanced technology and weapons around the world to liberate and empower people of African descent. T'Challa eventually beats Killmonger, and his demise was profound, with him preferring to die free like his ancestors rather than live as a man still bound to the chains of slavery in America.
Killmonger's story in Black Panther was so successful because he was a grounded and relatable antagonist. He's sympathetic yet unrelenting and challenges T'Challa's principles as well as physically. While his methods were wrong, Killmonger's motivations were clear and understandable, to the extent that Michael B. Jordan didn't see Killmonger as Black Panther's villain. He was a complex character and his story was done justice by director Ryan Coogler, but it reached a natural, satisfying, and meaningful end. If Killmonger returned to the MCU in the Black Panther movies it would betray the morality tale that was built into his original story and undercut the emotional significance of his decision to die.