Dr Hans Rosling made that prediction as he said Singapore has yet to feel the brunt of declining fertility and a rapidly ageing society.
If the babies do not come, this place will just fill up with old people, he said, tossing up the numbers that tell the story.
BACKGROUND STORY
HUMOROUS YET DEADLY SERIOUS
Dr Hans Rosling teaches global health at Sweden's Karolinska Institutet, which selects winners for the Nobel Prize in medicine, but is arguably more well-known for his humorous but 'deadly serious' lectures on statistics which he conducts worldwide and which are viewed by millions on the Web.
He co-founded the non-profit group Gapminder Foundation in 2005 with his son and daughter-in-law, which features a Trendalyser software that animates global development statistics, usually from the United Nations, to help people form a sharper view of the world. The software has since been acquired by tech giant Google.
He is married with three children and each has three children.
He was in Singapore earlier this month to give a lecture organised by the Royal Geographical Society.
With a total fertility rate (TFR) - or births per woman - of 1.2 last year, Singapore has one of the lowest fertility rates in the world.
Latest United Nations data puts Singapore's five-year average TFR at 1.37 for 2010 to 2015, compared with 2.57 in Malaysia, and 2.06 in Indonesia. Even Japan has a higher rate of 1.42 and South Korea, 1.39.
What it means is that by 2030, Singapore will have as many people above 75 years of age as young people below 15, and an ever shrinking number of young people will have to look after a growing number of elderly folk.
That is when Singapore will really need immigrants, to fill up the gaps in the population and to keep the economy humming.
Dr Rosling, a sought-after international speaker and Swedish global health professor and public statistics advocate, was in Singapore earlier this month to give a talk.
He was not short of ideas to encourage Singapore women to have babies.
On a previous visit two years ago, he said gender equality was key to fixing the great baby shortage, couples deserved more than four months' paid maternity leave, and Singapore men had to get more involved in child-rearing.
Relying less on foreign maids would do wonders for getting husbands more involved in raising their families, he felt.
Adding to that list on his recent visit, he said the baby situation would improve if more was done to erase the stigma of divorce or being a single mother.
'Allow women to divorce, give them favourable conditions... and you will get more marriages and children,' he said, though he acknowledged that this might be controversial in a society with Asian values.
Recounting a recent conversation in Hong Kong with an unmarried, childless Asian woman in her 30s, he said: 'I asked her, do you not like children? She replied, 'Oh yes, I do. It's the idea of a husband that I don't like.''
As the laughter from his audience died down, Dr Rosling pointed out that Singapore is not the only country with a falling birth rate.
Across the globe, as countries mature, people are having fewer children. Many couples stop at two.
The result is that the number of children in the world has stopped growing.
'The world has hit 'peak child',' he said, noting that the number of children in the world has hit 1.9 billion today and will likely maintain or dip slightly below this level from now up to 2100.
'People think the global fertility rate is somewhere around 3.5 births per woman, but in reality, that number is 2.4 today.'
Dr Rosling also emphasised that - contrary to what some environmentalists say about population growth aggravating climate change - it is not a growing number of people that is the major concern.
Rather, growing resource constraints will come from the existing billions in developing countries rising to the wealth and consumption levels of the richest countries.
Arising from this is the threat of war as countries jostle for land and resources, and also increased poverty due to the rising prices of fuel, fertilisers and food.
He accused some environmentalists of pushing 'a toxic combination of arrogant and ignorant views of the world' by saying the world would cease functioning if Asia began using as much oil as Europe and the United States.
'Frankly, I can live without the polar bear,' he said. 'But I cannot bear the thought of one billion people dying from terrible famines and wars.'
He said the solution lay not in controlling population growth, but in changing the way people live.
The world has the ability to harness technology and produce more food with fewer resources to feed a growing population - but there must also be a change in lifestyles.
This includes getting people to eat less meat, consume fewer goods and buy products that have a minimal impact on the environment.
Clearly someone who loves children, Dr Rosling said: 'People use the term 'population explosion', which I find severely derogative - you are calling a loved child a bomb!'
Life is more meaningful with children, he added. People and governments must weigh the trade-offs when people choose to have fewer babies.
'What is it that makes a society choose a brand-new luxury car over one more child?' he asked.
