The promise was moderate, to be sure. In the 1960s, Kim Il-sung, the founding father of the country and also father of the current dictator, promised that eventually all Koreans would eat rice (not corn or barley) and meat soup, live in houses with tiled roofs (not thatched), and wear silk clothes.
Every North Korean knows that even this moderate paradise has failed to materialize. However, the fact has never been admitted openly. In the past, economic difficulties and hardships, if mentioned at all, were always explained as they should be explained in a solid dictatorship, that is, by references to scheming enemies, above all US imperialists.