Wow...powerful stuff.
Logically, he's correct about the future birth demographics being skewed the way he suggests. Unless something dramatic happens, I don't see how that will change. There won't be a gradual blurring of the lines through - for want of a better expression - "marrying out", as Muslims are a very close community. You don't hear of many muslims marrying or partnering Western men/women.
As to whether the cataclysm he refers to, will happen, is much more up for debate. None of us really know.