On the more pessimistic end, AI will replace us and we'll be sent to the coal mines.
On the possibly most optimistic end, living standards are a composite of many things rooted in reality, so I'd say the actual cap is about doubling of life quality, which is not nothing, but not unprecendented if we look at the past century and a half.
There is no long-term time scale in which humans running things do not obliterate each other or end up sitting on a planet filled with trash.
Either we figure out how to colonize other planets or we hand over the reigns to something that can plan long term and not be irrational.
Maybe if we figure out immortality it might work, but with the short life span of a human there is no way to not be short-sited or eventually end up with the wrong person in charge the button.