Mysticsm and religion are returning because the promise of the Enlightenment and proclamation of the Rights of Man have never been realised and because science over-promised what it could achieve.
The European Enlightenment led to structured thinking about Man, Society and how the two interact that were entirely separate from God being involved - Man maknig his own rules. The greatest failrue of rational thought - from Paine thru to Marx - was to assume that rational argument (I'm not a Marxist or socialist but he makes a rational, logical argument if nothing else) would be enough to overcome the irrational side of humans.
Science would provide understanding about how, and Enlightened humans would be able to put that understanding to best use.
Unfortunately, the science managed to streak ahead of the 'enlightened' bit, and a bunch of chancers, assorted spivs and some vestigal bits of he feudal order managed to ransack industrialisation for their own ends, creating an industrial version of feudalism that we call capitalism.
And that's why we find ourselves in this strange world - part modern, part pre-modern, part post-modern. Unfortunately, the modern bits are controlled by those with pre-modern thinking, and the post-modern bits are largely irrelevant outside French academia and arguments on bulletin boards
Answering the original post...I see human history as a succession of cycles - not the pendulum or a circle, but a meandering waltz consisting of the same patterns (empires, top down hierarchies, war over resources for example) repeated in ever increasing complexity, with certain elements contained within them (human sacrifice as religious ritual for example) falling off. I have no doubt that what we currently call 'rational' thought and the Enlightenment will eventually fall back while newer forms of older structures, most likely based on religions will again come to the fore. But I also hold out the hope that there will be nations, or groups of people who will hold onto the ideas of Enlightenment so when the cycle comes round again it won't be starting from scratch...I would hope that eventually Religion and the Enlightenment thinking realise that their deepest teachings - tolerance, self sacrifice, care for others welfare - are the same and then, perhaps finally, the species will achieve it's potential.
Of course in that time we could wipe ourselves out in any one of a number of exciting ways, be wiped out by nature (massive vulcanism and mantle plume activity) or from extra-terrestrial origins (asteroid, unfriendly green dudes).
Or we could change our environment and evolve into something different...hell, we might even out-evolve the animalistic bits of our brains...
Who knows? All I do know is that we will repeat history - the old adage about failing to understand it and repeating it is happening right now.