The Justice League writer has given hints at the story he has been building in the pages of the relaunched New 52 title.
The first arc in Green Lantern, which has featured Hal Jordan and Sinestro, suggested the existence of a 'Third Army' that will be awoken by 'The First Lantern'.
"All the threats for the Corps have been external, and we're about to get to an internal one," Johns told Newsarama.
"And it's going to come at the worst possible time for the rest of the universe and for Hal and Sinestro."
Accused of being vague, Johns added: "How about... in the not-so-distant future. The Chamber of Shadows and freeing the First Lantern - all that stuff is coming down the line. I'm sorry. I don't want to give it totally away right now, because that's a pretty big story.
"In the next few issues, there are going to be a lot of intrigue and secrets revealed - and more questions asked. And it leads into the next story arc, which starts with issue #11 and is called 'The Revenge of Black Hand'."
The Third Army is thought to be an organisation created by the Guardians of the Universe to replace the Green Lantern Corps. The Guardians' first army was the Manhunters.
DC Comics has hinted at a forthcoming crossover event for the Green Lantern titles similar to the Batman-centred 'Night of the Owls'.
Green Lantern #8 will arrive on April 11.