Originally Posted by
Quinlan58
He's previously said the Warworld saga is "the biggest story he's told at DC", which would make it at least longer than The Last God (12 issues). Everything he's said so far implies it won't last further than 2022, which would (assuming it ends in December) make it around 15 issues long (plus Annual) at most.
Personally, I believe the arc after Warworld is Phantom Zone related. PKJ has reintroduced Aethyr, made mentions of a Sleeping God in an earlier vision and had the place in said vision be called the Necropolis (which relates to death, and thus phantoms).