There's at least two levels (Heaven and Hell) and likely at least three (Purgatory), so there's no real mystery about that "hint."
As for the darker consequences, closing the doors to Hell also means no one goes
to Hell anymore when they die, even those that richly deserve it. Same would hold true for Heaven, I imagine. But assuming you only close the doors to Hell, what happens to those souls? Evil, vindictive ghosts escalate maybe? They give birth to new, more dangerous monsters? etc.