The most obvious known Kirby DC creations are the New Gods, and they're being systematically souljacked by a mysterious silhouette that may or may not be the Infinity Man. Add to that Darkseid is shown repeatedly scheming with his chess pieces in what must be the most complicated Risk strategy ever devised, especially since it seems to include Holly Robinson as an essential factor.
Early Kirby creations the Newsboy Legion pop up in their original lineup to help Jimmy Olsen figure out why he has those Silver Age powers(the powers are actually pre-Kirby Jimmy Olsen, but his New Gods stuff started out in that series). Their fate is up in the air because even though Countdown declared "JIMMY OLSEN MUST DIE!", that's obviously not gonna happen. What remains to be seen is if Cadmus and their many, many clones will survive the character purge Final Crisis seems to be. Lord knows Kon-El didn't survive the last one.
Command 'D', the secret hideout of the Atomic Knights who debuted in The Battle For Bludhaven, was originally the name of the bunker The Last Boy on Earth, Kamandi, was raised in and named after. Kamandi was the last boy because most of the human race was wiped out in something only refered to as The Great Disaster. For casual readers, The Great Disaster has been a long standing plot device to explain why there are no superheroes or records of the past in the future. Kamandi was raised and trained in Command 'D' by his grandfather, Buddy Blank, the original OMAC. Makes that annoying blonde kid in Countdown more interesting, doesn't it.
With Countdown only half over, there's still 6 months for more of Kirby's inventions to pop up. That boom tube Waller and the government are using to deport super-villains is probably sending them to Transilvane, the planet in the basement. It's the perfect prison and probably where Ray Palmer's been hiding out. Maybe Atlas is the guy killing off the New Gods. As a titan, he would consider himself a 'real' god. And, God willing, maybe these guys would show up for the hell of it.