Let's say that one day, all of evolution was proven to be absolutely true. So much so, in fact, that every single person is convinced of it, and all religious people renounce their faith in their respective creation beliefs and belief in deities.
What would happen in the next 5 years? 10? 50?
Like Loudmouth said, it would be similar to the way we now view geocentrism as being clearly wrong and absurd.
And, like geocentrism, it would not necessarily make people lose their faith it would simply lead to a lesser emphasis on certain verses of the Bible and a greater emphasis on others.
For example, with geocentrism, the church used verses such as Joshua 10:12-13, Habakkuk 3:11, Psalm 93:1, Psalm 102:25, Job 28:24, Psalm 103:12 etc to support geocentrism and a flat earth.
However, once the church adopted heliocentrism, people re-interpreted those verses as "poetic" or "metaphorical" and the verses were given less ontological importance. Even good ol'
Answers In Genesis has a lengthy (and very scientific) discussion which ironically blasts the literal interpretation of Biblical geocentrism. The church even, hilariously, started touting the Bible as
predicting heliocentrism in Job 26:7.
This process is already occurring with Christianity and evolution. In the past, a literal interpretation of the creation story was commonplace. Today, more people are reinterpreting those verses to be poetic or allegorical. Verses that were previously used to support a literal creation are now being used to support evolution and
even being used to claim that the Bible predicts evolutionary theory.
That's a fairly long answer, but in essence, I think the proof of evolution will lead (and is leading) to a reinterpretation of the Bible on the same level as the reinterpretation that occurred with the acceptance of heliocentrism.
After this process is complete, what will be the next "big" thing which will fill the void left by the Creation-Evolution sub forum? I think as science delves more and more into consciousness, we may see a new debate which forces a reinterpretation of the afterlife. Believers will rail against the mounting evidence and the process will repeat.