Michael B. Jordan's Killmonger had a complete journey in Black Panther, and if he were to return to the MCU it would risk ruining his original story.
In an interview with TikTok user @theoriesbyt MCU star Michael B. Jordan hinted at the possibility of bringing his villainous Erik Killmonger back to MCU.
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.
Killmonger's motivations were clear and understandable, to the extent that Michael B. Jordan didn't see Killmonger as Black Panther's villain.
Killmonger was the opposite of T'Challa, someone who was willing and eager to break the rules and put aside all morality in order to get what he wanted.
In that context, bringing him back and essentially letting him win would be a betrayal of T'Challa's legacy.
The villain role for Black Panther: Wakanda Forever has not been officially announced, it's rumored to introduce Namor the Sub-Mariner as the antagonist, rather than bring back Killmonger.
Killmonger's return could be easily explained, but not justified from a story perspective, bringing such an interesting Villain back from the dead is tempting, but his story is better to remain finished.