That happens after the Christians disappear in chapter 3 iirc. And since we're all still here...
I'm not certain this hasn't already happened. Given that the vast majority of the people who practice Christianity as outlined in the Bible have virtually ceased to exist, that may well have come to pass.
Granted, I am not an expert on the work of fiction in question, so take that with a grain of salt.
"God is a comedian playing to an audience too afraid to laugh." - Voltaire