To even speculate that islam will overcome christianity is a sorry-ass joke. There are 2 -- exactly 2 -- major religions in terms of adherents. There are 3 christians for every 2 muslims. There are millions of rich christians for every rich muslim.
In my little ky town, there are hundreds upon hundreds of christian churches, while there is 1 islamic center with maybe 200 members (ie. a whole christian congregation or 2 for each individual muslim. Can you imagine the amount of pure chickenshittedness it takes to cry that we* should be afraid of the lunatic fringe of the amateurish islam.
The chicken little routine is an immense insult to christianity, its teachings, its followers, and the goodness at its core. Christianity outnumbers Mohammedanism 3-t-2. Christianity dominates nearly all of the world's major countries. Islam has never permanently replaced an advanced religion, government, culture, or economy. Islam apparently, based on where it thrives, is the self-destructive religion of the 4 horseman of the apocalypse. It is large because chaos reigns in many regions of the world, but it is incapable of coalescing into the thoughtful philosophical forms that rule the world.
If you believe that there will ever be a united states of sharia, or similar such dumb shit, then you are a loser, a traitor to your country, and an infidel to christianity. Mark it down. It ain't gonna happen.
We may get invaded by martians someday, but they are gonna have both christians and muslims for breakfast, lunch, and dinner.
* note -- I was raised a christian, and I still see the evidence of God in the world around me. I am philosophically a taoist (not religiously a taoist). In other words, I am not big on ritual and dogma. Therefore, when the battle comes I will be on the side of Jesus, with sword in hand, whether we are fighting klingons or islamofaschists. But to even pretend that these ululating fools are on the same plane as christians or americans is a humiliation that we should reject with all our might. Otherwise, we will lose . . . to our fearstricken selves!