The Bat-God thing was epic, but no, if Johns or any other writer tries to reveal the Joker's true identity then they are in fact an ass (in my opinion). When you reveal the reality behind the Joker he will cease to astonish us.
The thing that makes the Joker a classic is that he represents to the ordinary citizens of Gotham (us) exactly what Batman represents to the criminals of Gotham. He is an unknown that can show up at any point and ruin whatever plans you made. He's an enigma that poses a real threat to your existance. Now who I'm talking about depends on if you're a law-abiding citizen or a criminal, but either way there is only one answer to who "He" is. Revealing Joker destroys that. It makes him just another Cobblepot or Zsasz.