In 'The Plato Papers' I wanted to get another perspective on the present moment by extrapolating into the distant future. So in that sense, there's a definite similarity of purpose between a book set in the future and a book set in the past.
People who try to predict the future by extrapolating in a line of more of what exists - they are always wrong.
I'm not much interested in extrapolating science and technology; I merely use extrapolation as a means of putting people into new quandaries which produce colorful pressures and conflicts.