Dystopian Justice League?
What would happen if the Trinity got wiped out? In my head, losing your three biggest players to a tragic and violent circumstance, would probably Crush the team. I can see them trying to struggle on, but the constant barrage of villians would eventually wear down even their strongest, The Flash, Green Lantern (All of them perhaps) and even the Manhunter would all succumb.
In a world where the Heroes have fought, died and almost been eradicated, this is the team that I can see emerging from the ashes, desperately trying to save Humanity from itself.