她的健康每况愈下，可能不久于人世。 She is on the decline, and may die soon.
他将不久於人世。 He is not long for this world.
我上次见到他以后已过去二十多年了，他当时就已经上了年纪，我想他现在已不在人世了。 It is over twenty years since I saw him, and he was pretty elderly then; I shouldn't think he's in the land of the living now.
