what is hapenning is that white, WASPs stop breeding for all the reasons mentionned in this thread, but arabs, muslims, south americans and black dont. Which means white people who reached some kind of peak self consciousness/ intelligence level at some point stop wanting to live/reproduce. White people will get replaced by third worlders who are for the most part still "believers" (believe in their revenge against the old dying corrupt white man) but once these people live the same lifestyle as we did in our lands, they ll become materialistic atheists and will abandon their faiths to follow in the exact same path white people did, that's the irony. Basically the decline of white people -and interestingly japanese people- might in fact announce the beginning of the end for all mankind, people simply stop wanting to reproduce anymore at all once they ve reached full consciousness of the absurdity of life.
The Childfree religion taking over most belief systems until there are no humans anymore. Who would have thought mankind could simply disapear due to a lack of will to live. Forget about asteroids, solar flares, pandemias, global thermonuclear wars, we might actually simply not want to live anymore before any of those happen.