Following yesterday's announcement that the Wonder Woman Blu-ray will feature a short titled Etta's Mission, featuring Lucy Davis as Etta Candy, the actress revealed that she's definitely not finished with the character yet.
It is not immediately clear whether her next appearance will take place in real-time or in flashback, given that Wonder Woman took place in World War I but Diana was next (previously?) seen in Batman v Superman: Dawn of Justice, which took place in 2015.
"Learning new Etta lines while on holiday this week!" Davis tweeted late last night, quoting ComicBook.com's story on Etta's Mission. Since the Blu-ray will be out in a month, though, the lines she is learning are obviously not for the "Epilogue."
Recently, Geoff Johns revealed that the Wonder Woman script is currently being written, with the film expected to be produced in 2018 for a 2019 release date.
The most likely scenario, then, is that Davis has seen script pages for Wonder Woman 2. There are scant details available on the plans for the sequel, though, and since Diana is the only immortal in the principal cast, there have been a lot of questions as to whether Davis and other members of the non-Amazon cast would even be alive whenever the sequel takes place.
There is also the possibility that Etta could appear in a flashback, either in Wonder Woman 2 or in basically any DC Extended Universe movie.