Peak "augmentation" seems to have been (believe it or not) the Microsoft era, complete with its "productivity suite" (except productivity has gone missing) and killer apps like the spreadsheet that is still a computing interface out of this world.
The demise of the MS monopoly came about by the exploitation of opportunities offered by interconnected computers with zero regard to lofty empowerment ideals. The role of the computing device has become to offer just enough attraction so as to extract value from the individual using it. Achieving that at scale has required the dumbification of the UI, removing any cognitive stress. Except, no pain - no gain.
If the hypothesis is correct a next generation of important (G)UI's may come about if and when the much delayed harnessing of the networked universe to augment individuals starts taking place. It might be driven by the challenges of the new stage we are in. Think of concepts to address information overload or managing online personas. Or it might facilitate emerging possibilities, eg interacting with local algorithmic agents etc.