It’s worth noting that we never actually saw Killmonger expire on screen. He was gravely injured after his final brawl with Boseman’s King T’Challa, who offered to attempt to save his life using Wakanda’s ultra-advanced medical technology. Killmonger’s iconic reply: “Why, so you can lock me up? No. Just bury me in the ocean with my ancestors who jumped from ships, because they knew death was better than bondage.”
A stirring request — but did T’Challa honor it? We did see him apply the same emergency medical treatment — a vibranium disc — to Killmonger’s wound that was earlier used to stabilize T’Challa’s CIA ally, Everett Ross (Freeman). Even if it had been imminent at that point that Killmonger would succumb to his injuries, we also know two things about Wakandan tech: That its march of progress never ceases, and that cryostasis has been perfected, as we’ve seen it used on Bucky Barnes (Sebastian Stan). Could Killmonger have been figuratively put on ice until such time as medical science could save him?
Of course, there is another way Killmonger could return, without … well, actually physically returning. Having partaken of the Heart-Shaped Herb to gain the power of the Black Panther in the first movie, it seems possible that his spirit could now reside — along with that of T’Challa’s father, King T’Chaka, and the other Black Panthers of yore — on the ancestral plane. Here, he could offer singularly unique guidance and advice to whomever takes on the mantle of Black Panther after T’Challa’s presumed death.