Perhaps Mckenna’s eschaton is neither the mushroom (that enlightens mankind) nor the mushroom cloud (that destroys mankind) but the discovery of how consciousness is connected to physics.
Physical objects only exist if there is an observer. And physical properties of objects vary based on the frame of reference of the observer. We take for granted the element of time in physics, but it is as much (or more so) a property of the consciousness of the observer as a property of physics.
If self-awareness (i.e. self-observation) is at the heart of being conscious, then all scientific experimentation is an extension of consciousness. But because we do not fully understand what consciousness is, the mind-altering effects of drugs like psilocybin are as mysterious to us as any of the “spooky” aspects of quantum physics.
I view McKenna as someone who opened the doors that future thinkers will be traveling through for centuries.
He viewed language as so critical to understanding—as a result it may require totally new forms of language to make real breakthroughs in many different areas.
The science fiction movie that best illustrated this type of approach was the 2016 movie “Arrival”.
https://www.amazon.com/Arrival-Amy-Adams/dp/B01LTHYE04