While Arrow will abandon the flashbacks to Lian Yu (or Hong Kong or Russia) after the upcoming season, the series will still flash elsewhere … including forward in its timeline.
Executive producers Marc Guggenheim and Wendy Mericle told IGN that the plan for season six will include more flashbacks to other characters' perspectives and possibly flash forward, like the season four's graveyard reveal. But Guggenheim added that unlike the tale of Ollie's missing years, the season six cutaways "won't be telling a serialized story."
And really, after the thud of the Hong Kong story in season three and last year's Lian Yu snoozefest, that's probably for the best.
Meanwhile, Legends of Tomorrow executive producer Phil Klemmer told Zap2it that "it would be a crime" if the series never had a chance to meet up with John Constantine. In the Earth-1 of The CW, the character is said to be in Hell. Many interpreted that to mean the character is unavailable to the television universe as Warner Bros. Pictures develops a Justice League Dark feature with the character as an anchor. Even when he appeared in the form of Constantine star Matt Ryan on Arrow last year, the producers warned it would be a one time thing.
But Constantine has a knack for escaping from "one time things."
Arrow and Legends of Tomorrow return in October.