DC's weekly, 4-issue Countdown: Arena ships in December, and the official site for the mini notes that a character (or characters) from JLA: The Nail will be among the denizens of the multiverse chosen by Monarch to fight it out with 2 of his/her alternate selves for the privilege of joining Monarch's army.
Dan DiDio points out in the interview at http://forum.newsarama.com/showthread.php?t=124768 that Monarch "needs one Superman, one Batman, a Wonder Woman, a Green Lantern, a Flash, a Blue Beetle, a Nightshade, a Starman, and a Ray," and since the Supes, Bats, WW and Green Lantern fight cards have already been revealed on the Arena site (with no Nail characters in these 3-way slugfests), my guess is that one of the three Flashes will be hailing (in this corner!) from the world of JLA: The Nail.
But wait! To make things (more) confusing, the writer of the mini, Keith Champagne, points out in the interview at http://forum.newsarama.com/showthread.php?t=126009 that "Monarch has gone through all 52 of the universes and when all is said and done, there's a character from every single one to be found in the pages of Arena." So...maybe the character(s) from JLA: The Nail will be appearing as non-combatants, in attendance only to cheer on their favorites. ("Superman! Get in close and...use your knees! He won't expect that!")