I think that finding extraterrestrial life would challenge many of the worlds popular religions. Take Christianity for example. How will Christians interpret Genesis after the discovery of life on other planets? Was Christ sent to other planets as well?
Most Christians who've actually thought of their faith, (admittedly, that's few and far between) have most certainly already reconciled their beliefs with this subject. Off the top of my head, I'd imagine a reconciled Christian would say:
1. Aliens are not in the Bible, but nothing says they don't exist.
2. The Bible is God's message to man, and surely the Aliens will have their own message from the same God. (Actually, considering the similarities of Earth's religions, wouldn't that be something?) I digress.
Point being, the search for God will continue forever. It's part of human nature, and is ultimately an unknowable equation. Even with a thousand known species, people will ask why we are, and that can often lead to "because you were made to be".
I think it's foolish to expect a mass awakening on the discovery of ET. It's not going to happen. You'll have a few that will alter their beliefs, a few that will go wacko (thinking crazy white haired dude from Contact here) and everyone else will just ponder it for a while and carry on.
