But talking to Newsarama, Keith Giffen said;
You know what? I’ll just say that this is the Justice League. But there’s no time travel involved. So everyone who thinks it’s time travel, that’s not involved.
And when we do explain it to you, one thing is going to jump out and go, “Oh no! Not that again!” But… trust us.
Not that again? Hmmm.
Not that again.
This is purely speculative and nothing else, but could it be that the Justice League 3000 are… clones? Clones of the original Justice League? Or some version of them through the centuries? They are the Justice League, tick, there’s no time travel needed, tick, and… well we all remember the Spider-Man Clone Saga. Oh no…