Going back to the original post – which quoted the opinion of a blackhat seo – I believe it was meant to express that blackhat seo will disappear.
IMO, this is true, blackhat seo in it’s former and current forms will disappear.
However, on-page seo will always be there in some form.
Also, regardless of what the search engine’s rules and methods will be in the future, there will always be people looking to find loopholes and game the engines.
Consequently, search engine positions will always be in a flux, and sites would do well to gain as much independence as they can.