Yes, these numbers are back-calculated as you say (anything else would be witchcraft). And as you say, there could suddenly be a breakthrough technology in twen

Yes, these numbers are back-calculated as you say (anything else would be witchcraft). And as you say, there could suddenly be a breakthrough technology in twenty years that massively increases life expectancy. But IMO this is very unlikely, because people die of such wildly varying causes (including lifestyle-induced diseases, accidents and even suicide) that it's hard to imagine what this sudden change could be. More likely we will keep seeing incremental change, disease by disease, steadily increasing average lifetimes. Biology and biochemistry is so bloody hard compared to any human tech, it's amazing we have come as far as we have today. People talk about curing cancer like going to the moon, just throw money at it, but that analogy is only accurate if you assume starting your space program sometime around 1870.