"Welcome to WONDER WOMAN 1984, Steve Trevor!" Jenkins wrote.
Trevor sacrificd himself in the final moments of Wonder Woman, much to the dismay of fans. Given the loose rules of the superhero genre, though, there was a chance that Pine would return. Wonder Woman 1984, the sequel, will take place nearly six decades later than the 2017 film, which took place during World War I. Diana (Gal Gadot) has a generous lifespan, and we know from Justice League that she'll live on all the way to present day. Trevor is human, but there are definitely ways that he might be able to circumvent his World War I death. (How did he die? He detonated a poisoned bomb in a plane that he was piloting. So yeah, he's definitely dead!)
Fans on Reddit are preemptively nervous that this version of Steve will be Diana's hallucination. In the comics, Wonder Woman/Diana is frequently pining over Steve, fantasizing about their life together. This could very well be her imagination.
Or, Per Screen Rant, Steve Trevor enjoyed a "rebirth" in the comic books. The goddess Aphrodite reanimated Steve and gave him brown hair (he usually has blonde hair), dubbing him Steve Howard. It gets a little complicated from there: Steve Howard eventually meets Steve Trevor, a version of himself from an alternate timeline. (Yeah, baby, we're talking alternate timelines!) Steve Trevor then kills Steve Howard, and there's only one Steve left. In the books, this storyline took place in the '70s, which, you know, gives just enough time for Steve to find Diana for Wonder Woman 1984.
The 2017 film notably didn't feature Aphrodite, but the sequel very well could. Thus far, the movie's cast include Kristen Wiig as the Cheetah (the villain), Gal Gadot, Chris Pine, and Pedro Pascal in an undisclosed role. The film is slated for a November 2019 release.