Though the search for Joker's body continues, the Coast Guard reports it's extremely unlikely that Gotham's most notorious criminal survived the crash.
~ Angela Chen, reporting The Joker's fate in The Batman/Superman Movie

These are villains whose fate is truly unknown because the author is not making any more stories or the TV show, movie, or video game is cancelled.

NOTE: This category only applies when the story was ended prematurely, not for cases where the ending was intentionally inconclusive.