Dark Knights: Metal was the crossover event splash from Scott Snyder and Greg Capullo that DC Comics published three years ago, that rather excelled at crossing over everything it could, from Challengers Of The Unknown to Sandman to Hawkman, while playing air guitar in the process. It began with the Justice League becoming a Transformer and ended with Jack Kirby's Source Wall being rent in twain. It certainly had scale. And sales.
The impact of the storyline continues most prominently in the Justice League titles, Flash and Hawkman, but I understand there have been talks for a sequel.
As it stands I am told that Scott Snyder will only write Metal 2 if Greg Capullo is available to draw it. Currently working on their Batman collaborations on Detective Comics #1000 and the only Black Label title that seems to be progressing, Last Knight On Earth.
But it's what follows that, which is at issue. Because Greg Capullo is also lined up to draw the sequel to Reborn, Reborn 2, with Mark Millar from Netflix/Image Comics.
And DC Comics may want a year or so more for a Metal sequel.
Scott Snyder has had a big overarching story plan for years though, at least through 2020, and the story which could be Metal 2 would be the way to bring that story to an end. But if Greg Capullo isn't available, it may still be published – just not as a separate mini-series and event, but as an endcap to his run on Justice League.
Odds are, however, that Metal 2 would sell a lot more. Leading to rumours that DC Comics working out how much they can pay to match Netflix.