Quantum Supremacy sounds amazing, like a blockbuster movie! One imagines a disjunctive change, with humans either assuming the mantles of wise, beautiful gods or being dragged, screaming, from their place at the head of nature by blank eyed quantum computing powered robot deamons.

But actually my understanding is that the people who are driving the Quantum Computing research agenda mean something fundamental which is very distantly related to application. Quantum supremacy will be declared when :

"But what quantum supremacy means to me, is demonstrating a quantum speedup for some task as confidently as possible. Notice that I didn’t say a useful task! I like to say that for me, the #1 application of quantum computing—more than codebreaking, machine learning, or even quantum simulation—is just disproving the people who say quantum computing is impossible! So, quantum supremacy targets that application." [http://www.scottaaronson.com/blog/?p=2943]

Also, the article doesn't point out that there are many people working on this internationally, there are groups in the UK and Australia which are developing differentiated approaches which have a strong chance of underpinning the technology for QS - preserving QBITs for long periods and creating large numbers of them which can be usefully manipulated.