These assumptions need to be questioned.
"One, it will be run totally on digital technologies, smarter and smarter, more and more interconnected computers.": "Totally" digital? What is the source of energy for these digital technologies? What types of devices are we using to access these digital technologies? Are the goods and services they are used to sell "totally" digital? Are we going to live in digital houses? Are we going to eat digital food? "Digital" is only one part of the Internet of Things: the author forgot about the "things".
"Two, it will be totally global and operate on a planetary scale.": "Totally" global? What units make up this global totality?--does this means that regions, nations, cities, and neighborhoods disappear? If not, how do these smaller units relate to each other? What about language and cultural groups? Where do competing religious views such as Christianity, Islam, and secular atheism fit into this global world?--will these all inevitably coexist harmoniously? If Europe can't even stay united, if Syria and Israel can't settle differences peacefully, if China and Taiwan can't agree on how many Chinas there are, how is this global unification "almost inevitable"? And what is the timetable for this "almost inevitable" global unit to emerge, since the League of Nations and U.N. haven't been able to create it in the last hundred years?
"And three, it will have to be sustainable, in its energy usage and its impact on the planet.": "Sustainable" as measured by what?--how did we go about determining what level of energy usage is sustainable? What type of energy is being used? Is this assuming that technology for energy usage remains static?--what about new sources of energy and new technologies for harnessing existing sources of energy? And how do we know what impact energy usage has on the planet?--how are we measuring this?
I'd start there.
Excellent questions that deserve real answers, not the usual rainbows and unicorns kind of answers. The ones you pose on the digital technologies are ones already in my head since my area is manufacturing, one of the only real wealth creators.