A distracting thought: isn't it striking how "real property ownership" has returned as a marker of better societal status? A mere 50-60 years ago, even working class could own (arguably not very nice) dwellings in coastal California etc.
The same development can be seen in Europe.
If I had to choose, I'd rather be an owner of 3-4 nice pieces of real estate than a highly qualified professional. This is a certain return to feudalism, in a sense.
As for your original idea: going from 600 to 700 is not a big deal. But the intermediate phase is going to be a big challenge. The first generation that enjoys the possibility of life extension to, say, 120, is going occupy their positions of power for a disproportionately long time and will need to be persuaded to step away; possibly in exchange for a lot of money.
Yet when we design an economic system by the exact same principle, people wonder why we get ten shrieking megaphones instead of a magical tidal wave.
Big difference going from 50 to 70; proportionally less going from 600 to 700, even if the world isn’t changing in a way that makes recent experience count for more than ancient experience.