Mark Millar is teasing a sequel "one of my most beloved Millarworld projects" on December 18 from Image Comics.
Here is his announcement video:
The perfect Holiday gift. The sequel to one of my most beloved Millarworld projects since the dawn of time. The twist is that you don't know what it is so you're in for a nice surprise on December 18th. Can you guess what Santa's going to bring? pic.twitter.com/TaoBFEIUDG— Mark Millar (@mrmarkmillar) September 18, 2019
Given his wording as "the" sequel to a Millarworld project, it would infer it's a story that hasn't had a sequel before. Millar has already announced-but-postponed plans for sequels to Nemesis, The Magic Order, Super Crooks, and American Jesus. The remaining Millarworld projects without a sequel are Wanted, MPH, the unfinished War Heroes, Unfunnies, Empress, Huck, Sharkey the Bounty Hunter, Reborn, Prodigy, Space Bandits, and Starlight.
Arguably Millar's "most beloved", by fans and sales figures, would be Wanted by Millar and J.G. Jones. Originally published in 2003 and 2004 by Image's Top Cow imprint, it was adapted into hit film in 2008. Millar has spoken loosely about ideas for a sequel, but has never announced anything concrete.
Image Comics' December 2019 solicitations are scheduled to be released later this month.