With news about the Wonder Woman movie, which I believe begins filming towards the end of the year, I have spoilers about that film and all three DC cinematic universes and how that could potentially give away the plot of the GLC movie.
So a lot of the events of each inform the future of each film as the Battle for Metropolis in Man of Steel is basically the whole basis on which Batman v. Superman is built.
BvS then leads to Suicide Squad as Amanda Waller points out that Superman is like a beacon bringing these people (super-people) out from the shadows. Batman's appearance more then likely inspires Joker's own return. Wonder Woman's appearance is meant to be the catalyst for the Justice League movie.
Squad could possibly apply to why Batman decides to stay out of retirement after dealing with Superman and Luthor, thus how we get a Batman film. With Captain Boomerang in SS, he could show up again in the Flash film. Also Aquaman is in Dawn of Justice, and the why could have something to do with his own solo film.
SPOILERS ONCE AGAIN
The Wonder Woman movie acquaints us with how she and Batman know each other over in BvS.
So what's this got to do with GLC?
This scene in particular:
During Zod's flashback, he makes mention of how he and the rest of the Phantom Zone prisoners tried to find a planet suitable for them to inhabit, and here we see a bunch of dead kryptonians.
Who killed them?
Are we suppose to believe that they just wandered out of their ship and just died? One of the kryptonians looks as if he had been impaled.
That's where the Green Lantern Corps comes in.
After the destruction of Krypton the GL, Tomar-Re, investigates to see if there were any survivors, knowing the kryptonians were a very intelligent race and escaped the planet before its destruction. Tomar-Re discovers the planet Daxam and the dead kryptonians on it, seemingly drained of their lives.
We go to the opening showing Hal Jordan's origin:
Meeting Abin Sur. Getting his ring. Becoming Green Lantern.
Fast forward to the present and see Hal Jordan has found a similar situation on the planet Aoran.
The villain of the film would be Evil Star who has the ability, due to his Starbands, to blast star-bolts and create energy constructs, and his minions the Starlings, with some of the Justice League villain like Starbreaker mixed in; Starbreaker has the ability to absorb energy to help make Evil Star immortal and making him even more of a threat to a Green Lantern, even killing a few. He's an insane serial killer committing acts of genocide.
It's a murder mystery in space as members of the Green Lantern Corps investigate Evil Star, who ensures his immortality through absorbing the lives of any life forms he encounters.
Now, articles I have read suggest this will be a "buddy cop" film in space with possibly two human GLs.
I sincerely hope not.
The best part of the Green Lantern is interacting with other Green Lanterns of different species. I kind of think of Men in Black on a bigger scale. While it is suggested we may be interacting with more Earth Green Lanterns I hope to see Hal (sorry John Stewart, maybe in the Justice League film…played by Mekhi Phifer? That's my pick) interact with the likes of an older Tomar-Re, Arisa, Sinestro, C'Hp, Salaak, Kilowag, Boodika, G'Nort, and Laira.
The impact this would have on the greater DC cinematic universe is on expanding the galactic side of the universe. As the GLs go about their investigation, we encounter numerous alien races. Not to mention the Khunds are responsible in part for Sinestro's fall from grace as their invasion of his home planet Korugar revealed his corruption. So hey, sequel potential right there!
There'd also be potential for movies showing other characters in the DC universe to build other franchises and see the other side of what it is like to be policed by the Green Lantern corps.