Jonah prophesied that Nineveh would fall. He didn't say "if you continue to sin," he didn't say "unless you repent." He just up and said that the city would fall. But the people repented (in a fashion) and it didn't.
Very correct.
In fact, I myself was wondering if there has been a delay in judgment, and last month, I found in my heart that I could feel like Jonah if God delayed. God chastised Jonah, because Jonah wanted (I believe) judgment to come upon Nineveh.
God may indeed give the world more time. We do not know the day or the hour.