"One reason we think it may work is that technological improvements should generate an abundance of resources."

This is already being seen in some contexts. For example, the portion of income Americans spend on food has dropped from 17.5% to 10.5% over the last 53 years. "Because of the overall rise in income, and the consistent shrinking of food prices adjusted for inflation, we actually have more disposable income than our grandparents did" [1]. It is likely that improvements in agricultural technology and food distribution have led to the 'shrinking food prices' contribution, seen in the US. This means that there is downward pressure on the actual threshold of what would constitute a basic income, and thereby supporting Sam's assertion.

[1] http://www.npr.org/sections/thesalt/2015/03/02/389578089/you...