Religious influence will never completely die out, but in the sense you mean it, probably in the next 20-30 years.
I'm a spiritual person, but it disgusts me how religion tries to influence government policy in a regressive way.
So I am allowed to have ethics so long as I don't allow it to influence society? Good to know.
^That's why religion will always have an influence on politics. Both, fundamentally, are statements about what the world is like and how it should be (statements in a different context, but still statements). Christianity seems like its on the decline right now, but that doesn't mean the country will be without religions, it just may have 330 million of them.