Both Connie Nielsen and Robin Wright are reprising Hippolyta and Antiope, respectively, for Justice League, and since Nielsen implied that they share scenes together, that likely means they’ll be seen far in the past given that Antiope was killed in Wonder Woman when the Germans attacked Themyscira.
Seeing those two in battle isn’t terribly surprising, but since a fair amount of time passed between when Zeus created the Amazons for humanity and when Ares killed the Greek gods, we can presume that this flashback takes place in that interim period.
Throw in the fact that producer Charles Roven revealed last year that the “Old Gods” will play a role in hiding the Mother Boxes, and it’s a good bet that we’ll see the Olympians in Justice League, even if it’s just for a few minutes.