Post-scarcity just means the rate of use is less than the rate of renewal for all used resources. In a sense, hunter-gatherers were "post-scarcity." The challenge is supporting our modern quality of life at our scale of population. I think enormous strides would need to be made (fusion energy + matter synthesis, ie Star Trek replicators) in order to achieve post-scarcity on a long enough timeline without changing any of the other parameters.