Superman, maybe. But Wonder Woman? People been assuming she's a lesbian since her creation, and DC has flirted with the idea before. Her being bi would make a splash, but far from a "sacrifice."It would feel like those character would be sacrificed on altar of getting some free publicity.
My Bet
At the end of the movie. The camera zooms back on Batman and Superman shaking hands to reveal that the viewer is looking through a magical lens suspended in mid air. The camera continues to zoom out revealing 5 other lenses. Each lens is a different scene. Wonder Woman on beach hugging her sisters goodbye and flying off into the distances. In space two emerald bolts streak toward earth. Barry Allen being hit by lightning. Vic stone lying on a operating table. Aquaman sitting pensively on his throne. Then the camera pans around revealing the location, the Rock of Eternity, and the aged Wizard Shazam. It ends with Shazams words "The Second Age of Heroes has begun"
I'd be down for this.