The notion that we ought to take everything seriously that is 'not impossible by the laws of physics' is entirely stupid. Because virtually anything is possible, the question is how likely it is, and what evidence we have for it that is quantifiable and meaningful. Or are you currently prepping for an alien invasion?
Myth is the absolutely correct label for 'superhuman AI' fantasies, because the difference between a real threat and a myth is that the former is grounded in empiricism while the latter is a product of psychology and storytelling.
And superhuman AI is a very old story, it's simply the Golem myth. The religious idea that humans, in their hubris, create a tool beyond their control. It's Goethe's The Sorcerer's Apprentice and it's The Terminator.
Also, Kevin Kelly the author of the article is the founder of the magazine.