4. Immortality is not as crazy a scenario as it sounds. All it requires is for technology to be advancing faster than you’re aging.
In principle, all you have to do is turn this line into a curve a little—increase this rate by a factor of four —and you have life expectancy advancing one year for every year you age. And you have something that looks like immortality for some people.
There is a fifth scenario, which will ensue if it turns out that medical science becomes an behaves like an information science: True immortality.
That would come about when the rate of life extension grows not on a one-to-one basis, but on an exponential curve as Moore’s Law requires. That would mean we’d see life extension on a ten or even hundred year basis for every physical year lived – although at some (relatively early) point in that curve, we would be uploading our minds to far more durable substrates than our physical bodies.