Even though Amazon's Good Omens series covers the entirety of the Neil Gaiman and Terry Pratchett novel on which it's based, a Season 2 isn't entirely out of the question. The limited series comes to a conclusive end, but Good Omens covers all of time and space, meaning there is plenty more story to tell in the battle between Heaven, Hell, and the humans caught in between.
In Good Omens, Heaven and Hell are about to engage in the war to end all wars, and all that's required is for the demon Crowley (David Tennant) and the angel Aziraphale (Michael Sheen) to make sure the Antichrist is at the right place at the right time. As fate would have it, though, this doesn't go according to plan, and the two decide to take matters into their own hands to keep the Apocalypse from happening. By the end, the two are ultimately successful, and they toast to the world. However, even though a neat bow was tied around Gaiman's story, there are hints in the finale that the Apocalypse was just the beginning.
Good Omens Doesn't Have A Sequel
Though there is plenty of potential to keep Good Omens' story going, considering its vast - even timeless - subject material, nothing exists at the moment on which a second season could be based. Neil Gaiman and Terry Pratchett published Good Omens back in 1990, amassing a strong following from both of the writers' devoted fanbases, and the novel has a complete beginning, middle, and end. That said, Gaiman and Pratchett had discussed the possibilities of a sequel, going so far as to come up with a title and some story elements.
The sequel they had in mind would have been called 668: The Neighbour of the Beast. However, as Gaiman previously mentioned that he had no plans of creating any more episodes after Good Omens' first season, and that the show even includes some concepts from the unmade sequel, according to Radio Times, it makes the chances of it ever happening less and less likely. That said, though, the end of Season 1 does suggest more to come.
Good Omens Could Continue With Season 2
In Good Omens' finale, after Crowley and Aziraphale make their sneaky escape from the clutches of Heaven and Hell, they sit in a park and chat about what's to come. And, though the Apocalypse might have seemed like the worst of their problems, Crowley reminds Aziraphale that this is likely just the beginning, that their post-Apocalypse downtime is "breathing space before the big one." Aziraphale isn't entirely convinced, believing the Apocalypse they just prevented to be the final attempt at ending the world, but Crowley believes that the next war will be "all of us against all of them;" or, in other words, Heaven and Hell versus Earth.
On one hand, this hint at potential doom could just tie nicely into the inevitability of God's "ineffable" plan, but on the other hand, it could be a safe move on Gaiman's part, leaving room for a potential sequel, assuming ratings and a stroke of inspiration are on his side. Whatever the case may be, the first season of Good Omens ends on a high, and embracing the simplicity of a limited series might work in its favor. That said, when it comes to what decision Amazon will ultimately make, God only knows.
Good Omens is available to stream on Amazon Prime.
Source: Radio Times