[WARNING: This post contains POSSIBLE SPOILERS for Star Wars: Episode VIII]
One of the most talked-about sequences in last year's Star Wars: The Force Awakens was Rey's Force vision. Upon touching Luke Skywalker's old lightsaber in Maz Kanata's castle, the scavenger-turned-Jedi saw a disorientating series of images that raised even more questions about the 30 years between Return of the Jedi and Episode VII. It seemed to combine the backstories of Rey and Luke, showing the elder Jedi Master saying farewell to his companion R2-D2, while closing with a young Rey begging for her family to come back.
From this, fans could gather the basic outline of what happened before Rey landed on Takodana. Luke was attempting to form a new Jedi Order, and when Ben Solo turned to the Dark Side (becoming Kylo Ren), everything went to hell. In the aftermath, Kylo formed the Knights of Ren and Luke went into self-imposed exile, hiding a map to his location in Artoo. Those who wanted to see more of the Force vision might be in luck, as it could factor into Star Wars: Episode VIII.
The latest rumor comes from Making Star Wars (a reliable source that got many Force Awakens scoops right), saying that director Rian Johnson has planned a continuation of sorts that reveals more of what happened. Per their sources, there's a sequence that involves Luke, R2-D2, Kylo Ren, and a collection of dead bodies (said to be trainees of Luke's massacred by Kylo Ren). Rey is part of the scene as well, but the report indicates that Rey is merely a bystander and inactive, hinting that it could be another vision of hers. Their write-up was brief, so details are scarce for the time being.
It's worth pointing out that during production on The Force Awakens, props of lightsaber hilts were made specifically for dead Jedi apprentices (Making Star Wars has a photo of one), implying that this is something J.J. Abrams was going to tackle at some point in that film's development. Lucasfilm very well could have decided to save certain elements for a future film instead of revealing everything at once (see: Maz's answer when Han Solo asks where she got the lightsaber). The Force vision had enough to dissect in Force Awakens as it is, and the studio probably didn't want to overwhelm the audience. Now that the sequel trilogy has firmly been set up, the filmmakers could be open to returning to previously discarded ideas.
One thing that is becoming clearer is that Episode VIII should feature a heavy dose of Rey, Luke, and Kylo Ren - a tantalizing conflict for fans to consider. Earlier this year, Mark Hamill, Daisy Ridley, and Adam Driver were all spotted filming in Ireland, the location used for the planet Ahch-To (where Luke is found at the end of Force Awakens). With Star Wars 8 serving up a meaty role for Hamill, Skywalker's interactions with both members of the new guard should be fascinating to watch unfold. He obviously feels tremendous guilt over what happened with Ben Solo, and might be wary of training Rey due to his insecurities as a teacher. Viewers are eager to learn the full extent of Luke's history and Episode VIII should answer most of the queries.
Rogue One: A Star Wars Story opens in U.S. theaters on December 16, 2016, followed by Star Wars: Episode VIII on December 15, 2017, the Han Solo Star Wars Anthology film on May 25, 2018, Star Wars: Episode IX in 2019, and the third Star Wars Anthology film in 2020.
Source: Making Star Wars