People have been talking about the vacuum that Christianity has left or will leave in Western society for over a century. Most of the time, however, those who complain about this then completely miss the point.

The new organizations, ideologies, and new-age pseudo-religions "filling the religion-shaped hole" in society aren't inherently "lesser" than religion (or necessarily better). They are simply filling the niches in an ecosystem that many traditional religious structures by and large refuse to adapt to.

Yes, the sudden decrease in religiosity in society is probably just trading one set of problems for another, but if individuals didn't think that leaving their church was in their best interests then they wouldn't have left in the first place. Secularization is an inevitable consequence of freedom.

Religion and Christianity itself probably won't ever go away for the same reason it has clung to life for millennia: it will change and adapt to those new needs. It's only the stubbornly complacent sects and congregations who will dwindle and go extinct.