Demographics: 10 billion, mostly old people. World population will stabilise at around 10 billion people, and they will be increasingly old. An average age of 55 is not unreasonable by 2100. Longer lifespans will bring more people back for second and third dips into tertiary education, or indeed continuous education. Overall, the sector might be ten times as large as it is today. It is not unreasonable to suppose that a large portion of the population over 18 might be engaged, in some form, in tertiary education.
Economics: The end of scarcity. A continuation of the 20th century trend would bring another tenfold increase in per capita GDP, making the world, on average, as rich as todays richest country (Norway). Only people at the very margins of society will be unable to afford tertiary education. In the first half of the century, vast cohorts in the old 'Third World' will want, and be able to afford, University educations.
Telepresence: The Death of Distance. Increasingly compelling, immersive and reliable telepresent environments will render the idea of bringing people together in one physical space for education or work a quaint anachronism. Teams or classes may come together once or twice a year, for novelties sake, but true telepresence will make geographic distance as old fashioned an idea as posting personal correspondence in physical mail..
Artificial Intelligence: Smarts too cheap to meter. The steady process of Moores law will create machines with processing power to match the human mind relatively early in the century. Distributed processing will allow systems to draw on immense processing power when needed, and present machines as cheaper alternatives to most jobs currently done by humans. User interfaces that can pass a Turing test will make machine staff indistinguishable from humans. Why hire a human receptionist to answer the phone when the phone comes a processor that can do the job, that doesn't need coffee. When a 1000 euro machine is smarter than anyone you can hire, why hire anyone? The consequences for economics and employment is staggering, and managing the transition will be a huge issue from mid century on.
These are simple extrapolations of well established trends, none of which have any major roadblocks in sight. It's difficult to make a compelling case against any of them. As of 2010, these trends have massive inertia behind them -it's difficult to imagine what scale of events could derail them.
That's not to say that nothing else will happen. Few in 1900 would have predicted the ubiquity of Automobiles, air travel or the Internet. But in 1900, the key trends that set the tone of the 20th century - population growth, economic growth and urbanisation, were in motion. Geopolitical events (like the world wars) could not have been forecast in detail, but the logic of industrialisation made it inevitable that great power wars would get bigger, and worse, until they became so destructive and expensive as to be not worth the risk. We could not have predicted the 747, but we could have predicted that economic growth would have made international travel relatively cheap and easy - we might have predicted a super Zeppelin.
Having mapped out these trends, the challenge now is to figure out what the consequences of these trends are for Tertiary Education, not just in isolation, but as these trends interact and interlock. The second challenge is that the future is not path independent. We don't just wake up in 2100, with institutions and people perfectly attuned to it, no more than our institutions and peopel in 2010 are perfect fits for the world today. As the century plays out, existing institutions will adapt, or maladapt to the changes. Peoples ideas and preconceptions will change, but only in generational slow time. The future is not a destination everyone arrives at once, it's kind of smeared out, as William Gibson said:
"The future is already here. It's just not very evenly distributed"