Susan, I have a lot of respect for Peter, but on this issue I believe he is completely wrong. I see absolutely no threat whatsoever. For what it's worth, here's my take.

1) Most of the emerging economic world powers have very small Muslim populations - specifically, China, India, Brazil & Russia (also known as the BRIC countries - I ordered them by population).

2) I have no quarrel with religion of any kind, but the truth is America's way of life is not a function of Judeo-Christian society, but a function of education and science. The period of time when the Christian Church dominated society was known as the Dark Ages. They didn't call it that because it was dark. For better or worse, no religious leader ever invented a computer or figured out how to send a man to the moon. A society dominated by the Muslim faith (or any other) could never match the accomplishments of a society of education and science.

3) I've known many Muslims in my lifetime & they are no different than Christians - some are strong believers, some less so. Of course, a small minority of Muslims are radical. A small minority of all peoples are murderers - that's why we have police.

4) The further in the future for any prediction, the less likely it is to come true. I've never seen any prediction 30 years out that's been even close.