"The first person to live to [200, 300, 500, 1000] has already been born"

[Amine]

It's just a matter of time? What does that mean, like a million years? A billion? This is vague, and fatalistic. It's "a matter of time" particularly if we don't develop this technology. Why bother with anything at all? We all die in the end, right?

Far less than that.  It means that if people stopped dying, and continued to breed at current rates (or, lets softball it, 3rd or better generation first worlders rates) we would simply run out of stuff.  I know, there's "stuff" out in space....but getting it here is non-trivial, and were pretty far away from that.  Granted, the notion of global mobilization into space is more palatable than global sterilization.

Why would we run out of stuff? There are nascent technologies such as

-Nuclear, solar, wind (etc) energy
-In vitro meat (livestock farming is an immense drain)
-Desalination
-Distributed manufacturing, aka 3d printing, followed by...
-Nanotechnology with extraordinary capacity to recycle matter
-Advanced transportation or the complete lack of need for transportation due to telepresence

..to name a few, which are going to usher in an era of abundance, not lack. That's why poverty in the world is already decreasing drastically. The carrying capacity on this planet alone has a long way to go.