I don't think they'd replace him. They'd move on to another villain(s): The Riddler, Catwoman, The Penguin, etc.
How can a villain just disappear without any resolution? Batman left him alive and he wasn't captured...
Long as I remember The rain been coming down. Clouds of Mystery pouring Confusion on the ground. Good men through the ages, Trying to find the sun; And I wonder, Still I wonder, Who'll stop the rain.
