The UN tracks population data and these are available for viewing on Our World In Data.

https://population.un.org/wpp/Download/Standard/MostUsed/

We can use population life expectancy to track reduction of global poverty, inequality, and resource scarcity. In a post-scarcity economy, we might expect life expectancies in economically disadvantaged countires to accelerate beyond those in advantaged countries.

The country with the highest life expectancy among all large countries (>10.0m population in 2019) is Japan. Japan had a life expectancy of 84.4 prior to the pandemic in 2019, 11.6 years higher than the World life expectancy at 72.8.

If trends over the last 20 years are projected into the future, and assuming life expectancies shortened by the pandemic will bounce back, this gap will converge from 11.6 years in 2019 to 7.1 years in 2050.

If life-extending treatment and technology invented between now and 2050 is generally easy to access, life expectancy across the world may converge faster with leading countries than projected. On the other hand, if new treatment and technology is generally expensive to access, life expectancies in leading developed countries could accelerate beyond general world life expectancies.

Some prediction markets suggest a future acceleration in life expectancy growth, perhaps due to medical breakthroughs driven by artificial intelligence.

https://www.metaculus.com/questions/6592/when-will-a-country-reach-escape-velocity

https://www.metaculus.com/questions/12681/life-expectancy-at-birth-in-the-g7

This contract resolves YES if the 2050 life expectancy of the world's leading large country (over 10.0m population in 2019) is less than 5 years ahead of the 2050 world life expectancy, according to estimates at UN Department of Economic and Social Affairs Population Division, or other appropriate UN body; otherwise the contract resolves no.

Jan 29, 12:07pm: Global poverty: Will world average life expectancy converge to less than 5 years of the leading large country's life expectancy? → Global poverty: Will world life expectancy increase to less than 5 years of the leading life expectancies?

Mar 4, 11:59am: Global poverty: Will world life expectancy increase to less than 5 years of the leading large country's life expectancy? → Global poverty: Will world life expectancy increase to <5 years of the leading large country's life expectancy by 2050? (edited question to be less ambiguous and better fit the fine print)