re: Arkham Knight trailer

vengeance/revenge/whatever was also mentioned in the trailer

I think they were referring to Arkham Knight, which would make sense if it were Jason Todd, especially coming at the end of the series, joker dead, and ra's al ghul's involvement in "city"

I also think ra's al ghul will return...his body was gone from the gate where he was impaled.

I think scarecrow plays a role similar to hugo strange (being used by al ghul) and arkham knight plays a role similar to joker in city (not behind the overall plot, but still the main villain...al ghul wants revenge for talia) just spitballing