Follow-ups
A brief addendum appeared in Solo #5 (2005), a collection of short stories written and drawn by Darwyn Cooke. One of the stories, featuring King Faraday, is set in pre-revolutionary Cuba and is titled "Triangulation: A New Frontier Thriller."
In time for the DTV release of the animated adaption Justice League: The New Frontier, Cooke and DC Comics released a follow-up special titled Justice League: The New Frontier Special as a tie-in as well as adding more stories onto the comic version. Stories included a Batman vs. Superman that revealed that it wasn't until the mid-1950s that Superman and Wonder Woman met Batman, a post-New Frontier story where Robin teams up with Kid Flash for the first time as well as a Mad Magazine style story between Wonder Woman and Black Canary.
Read more about this topic: DC: The New Frontier