At the time of Justice League’s release, we assumed Diana was indirectly referring to how Steve Trevor sacrificed himself aboard that plane to destroy Doctor Poison’s deadly gas in Wonder Woman, but now we know that she has one last encounter with him in Wonder Woman 1984.
Again, we don’t know how Steve has popped up in 1984 and what he’ll be doing, although Patty Jenkins has assured fans that this indeed Steve and not someone in disguise, a hallucination, etc. That leaves resurrection on the table, and since Wonder Woman 1984 is pulling from the mystical/mythical realm like its predecessor, it’s easy enough to imagine powerful forces being harnessed to bring Steve back, and in era-appropriate attire no less!