HBO will wrap its wildly successful Game of Thrones series in 2019 with an eighth season, but the network isn't leaving behind the world of Westeros just yet. The company has already set in motion several prequels, one of which is coming from A Song of Ice and Fire author George R.R. Martin and screenwriter Jane Goldman (Kick-Ass). According to Martin, though, not all of the potential prequels will make it to production.

"As for the other successor shows," Martin wrote in a blog post, as The Hollywood Reporter points out, "if you have been following along, you know that we started with four, and eventually went to five. One of those has been shelved, I am given to understand, and of course Jane's pilot is now moving to film. But that does not mean the others are dead."

Martin did not specify which of the possible prequels had been cut, and when contacted for comment HBO told THR that “no decisions have been made.”

So far, HBO has green-lit an untitled prequel by Goldman set thousands of years before the time of Daenerys or Jon Snow that illustrates “the world's descent from the golden Age of Heroes into its darkest hour. And only one thing is for sure: From the horrifying secrets of Westeros’ history to the true origin of the White Walkers, the mysteries of the East to the Starks of legend...it’s not the story we think we know."

But that’s only one of multiple spinoff projects HBO is incubating. There’s another by current GOT writer Bryan Cogman, one from Westworld writer Carly Wray, another from L.A. Confidential writer Brian Helgeland, and one from Max Borenstein, who penned Godzilla and Kong: Skull Island. Martin writes that only three of those four spinoffs "remain in active development."

"Everything I am told indicates that we could film at least one more pilot, and maybe more than one, in the years to come," Martin wrote. "We do have an entire world and tens of thousands of years of history to play with, after all. But this is television, so nothing is certain."

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Martin isn’t wrong. So far, Goldman’s series is the only certainty thanks to an official pilot order. The spinoff doesn’t have a name yet, but Martin did offer on possible title. "My vote would be The Long Night, which says it all, but I'd be surprised if that's where we end up,” he wrote. “More likely HBO will want to work the phrase 'game of thrones' in there somewhere."

Though he’s helping with the pilot, Martin says most of the work is being done by Goldman as working on A Song of Ice and Fire's sixth book, The Winds of Winter, is his "top priority." He went on: "It is ridiculous to think otherwise. If I wasn't busy with Winds, don't you think I'd be scripting one or more of these pilots myself? It's not as if I've never written for TV..."

It’s unlikely we’ll know much about these prequels until they actual manifest on our screens. The final season of GOT airs next year, but there’s still very little info out except for the fact that the series will reportedly add at least eight characters in the last six episodes and feature an epic battle scene that took 55 nights to shoot.