A manned mission to Mars, Facebook on a fold-up screen, burned-out parents and the dubious honour of being the first generation who will be worse off than their mothers and fathers: a glimpse of the future for those entering the world in July 2013.

On the day the royal baby settled into his crib for his first night's fitful sleep, more than 2,000 other lives began in the UK on a journey that will take a third of them to their 100th birthday.

Average life expectancy for babies born now are almost 79 years for boys and 82 and a half for girls. But what can they expect in that lifetime?

By the time the royal baby is 22, there will be more hundred-year-olds in Britain than the population of Exeter today, and they along with everyone else will be talking more and more about the weather. The government predicts there will be more deaths in heatwaves and large-scale water shortages, even though well over 3 million people will be at risk of flooding by the middle of the century.

In medicine, genetic testing will radically change the treatment of serious illness. Simple tests will be able to predict life's big changes – some we want to know about, like the menopause, and others, for example the likelihood we will contract incurable dementia, we may rather not.

Online interaction will become an almost invisible phenomenon, channelled through screens in clothing, on wrists, in spectacles and through more conventional tablets and phones, say technology experts.

"It will be like asking a fish to describe water," said Benedict Evans, a telecoms and media analyst. "It is something you live in and are sustained by."

Downing Street has been looking ahead on our behalf and one arresting conclusion seems to be that the recipe for staying happy looks set to become more complex than ever.

More two-income families, a greater need for adults to look after ageing relatives, rising competition from China and India, a constant revolution in technology and the winds of migration making the UK an ever more diverse place, will all test the mental wellbeing of those born in the latest generation, the Cabinet Office's future-gazing programme has concluded. It is an opportunity as much as a risk, they say, but it is hard to avoid the sense of mild gloom.

Whitehall is not alone. Over the last couple of years, social indicators have started to show improvements in quality of life are going into reverse for the majority, according to Professor David Gordon of the University of Bristol's school for policy studies. So when the new generation flick through their parents' photo albums showing foreign holidays, shiny new cars and university graduations, amusement at the old styles is likely to be offset by envy at the relative wealth of their parents' upbringing.

"They will be the first generation in living memory that will face bleaker prospects than the previous one," said Gordon. "Incomes aren't growing for the majority of parents, the quality of schools is falling and healthcare is likely to get worse. Growing up in the sixties wasn't as nice as growing up today, but we may be going into reverse. I hope I am proved wrong."

Unicef this year ranked the UK 16th out of 29 developed countries for child wellbeing, behind France and Germany as well as Portugal, Slovenia, Ireland and the Czech Republic. The analysis was based on measures of material wealth, health, education, housing and behaviour, such as how much exercise children get, whether they take drugs and even how much they fight.

On the bright side, children are better treated by their parents than 40 years ago, the concept of children's rights is well established and children are better protected against abuse than they have ever been.

It may be the change in parenting attitudes that matters most. William and Kate are among a generation shaping their families differently to their baby boomer parents. They are often both working, caring for their own ageing mothers and fathers – frequently at long distance – and bringing up their own children in family units that include more step-siblings and more single parents, said Claire Halsey, a clinical psychologist and parenting expert.

"Balancing trying to be the best parent you can, a good spouse and a good son or daughter, parents often have a sense they are not getting it right when they often are," she said. "What happens time and again is that parents don't look after their own relationships and their own lives as adults."

Research on the consequences of these stresses on offspring is still developing, but "there are more behaviour issues now than 20 year ago". Children are often less prepared to start school and more happy to challenge authority in a disruptive way.

Grandparents will be involved in more and more of the childcare – a good thing, says Halsey, because it gives children a greater sense of belonging to a wider family network and access to the wisdom of older generations. Perhaps they can tell the little ones what a compact disc or a pixel looked like.

"This is the generation that will never tune anything into a channel, they will never buy a disc or cartridge, they will never use a landline," said Evans.

Classroom exercises will be done on screens loaded with software to alert teachers when a certain pupil is struggling. Life will be "saturated by videos".

Rather than living through a new revolution in computer technology, the next generation is poised to master it. They will, according to Aleks Krotoski, an academic and writer, become more sophisticated and critical in their consumption of the web and develop a subtle etiquette around social networks. For example, they will respect that embarrassing things people posted years ago should be treated with a sense of fade that human memory allows but software does not.

"It will be instinctive, because they have grown up with it," she said.

Work will become more polarised, with increases in high- and low-paid jobs at the expense of those in the middle, according to a study for the Joseph Rowntree Foundation.

For the poor, it will be more precarious. A lowering of expectations about employment rights during recent austerity will stick, with catering, cleaning and care workers increasingly on weekly or monthly contracts, on-call and on minimum wages.

One thing the next generation need not fear is growing old alone. By the time they are in their late 50s, the over-65s will have doubled to nearly 21.3 million, while those over 80 could more than treble to 9.5 million, government figures suggest.

Failure to harness their mental capacity and to shrug off negative stereotyping of old age could, the government warned, cause "a spiral of poor wellbeing, mental ill-health, exclusion and disenchantment in this large and growing sector". The dark cloud of dementia will loom large. Over the next three decades the number of people affected could double to 1.4 million.

But tomorrow's adults will set their sights on ever more ambitious horizons. Private companies and Nasa are planning manned missions to Mars – a mere 501-day trip – so while commuting by jetpacks and flying cars may still be a long way off, the royal baby generation could yet take its own giant leap for mankind.