Earlier this week, Entertainment Weekly confirmed something Game of Thrones fans had long suspected, and author George R.R. Martin had previously hinted. Bryan Cogman, executive producer and writer on the HBO series, is working closely with the author to pitch the fifth potential Game of Thrones “successor show”—what everyone else is calling a “spin-off.” After that official announcement, Martin himself took to his blog on Wednesday to add some extra hints about the still-mysterious project. HBO has yet to reveal the actual content of this or any other proposed Game of Thrones follow-up—but Martin’s clues may make it possible to figure out what he and Cogman are planning.

“You should not expect to see all five shows, though, at least not immediately . . . much as I might love the idea,” Martin wrote on his blog. “But we could possibly see two or even three make it to the pilot stage, with one series emerging on air in 2019 or 2020 . . . and the others maybe later, if they come out as well as we all hope.” Martin also announced over the summer that his next book, the Song of Ice and Fire-adjacent history Fire and Blood, Volume 1, has been set for publication in late 2018 or early 2019.

The timing here could very well be a coincidence, and Martin is notorious for setting deadlines for himself—then blowing right past them. But these dates could also reveal what, exactly, Cogman’s spin-off series will entail.

Martin initially intended Fire and Blood (also jokingly known as the GRRMillion) to be a complete history of House Targaryen, with a heavy focus on all the Targaryen kings from Aegon I to Aerys II. In 2014, Elio Garcia, Jr., one of Martin’s co-writer for The World of Ice and Fire suggested that he wouldn’t complete the Targaryen book until after he had finished the long-awaited final two books of the Song of Ice and Fire saga. But while writing the more complete Westerosi history for a separate companion book, The World of Ice and Fire, Martin found himself focusing more and more on the Targaryen kings, to the point where the book couldn’t accommodate everything he had dreamed up. In total, Martin reported editing out over 200,000 words from The World of Ice and Fire—words that he reserved for Fire and Blood, which (until earlier this year) was slated to be published after the main series finally concluded. But then Martin announced in July that he actually planned to split Fire and Blood into two parts, and that the first—which was “largely written“ already—would be released as soon as 2018.

Martin has good reason to run to the printer the moment he finishes something; the HBO series has long since blown past his own Ice and Fire books, and though the author has never critiqued the show directly, watching other people finish his story has clearly pained him. Look at what he said about why he did not want HBO to adapt his Westeros-set Dunk and Egg novellas, at least not immediately: