Justice League planted seeds for all of its heroes to have interesting journeys in standalone films but none more than the iconic Flash story Flashpoint.
Some spoilers for Justice League follow.
While visiting Henry, Barry revealed his plans to become a crime investigator as a means to free his father from the false conviction of murdering his mother and Henry's wife, Nora.
The Flashpoint comic's story centered around bringing Nora Allen back to life by means of traveling back in time to prevent her murder. In doing so, however, Barry completely shifts the timeline of the world he once knew, and begins to forget everything as he develops new memories from the new timeline. Nearly everything has changed in the new timeline, including the identity of Batman, as Bruce Wayne was killed as a child and Thomas Wayne dons the cape to avenge him.
Furthermore, the conversation between Henry and Barry had a metaphorical reference to the time travel events of Flashpoint.0comments
When Henry asked Barry to stop coming to see him and abandon his wishes to become a detective, he pleaded for Barry to only run forwards, into the future, and stop running to the past. In Flashpoint, Barry literally runs to the past!
Following Justice League which is now playing in theaters, Aquaman will release in December of 2018, follow by Shazam and Wonder Woman in 2019. While there are many more DC Comics films in development, Flashpoint is likely next in line.