It seems to me that sci-fi most often merely elaborates on the present. In fact, the inclusion of the "sci" part is incorrect, as very few sci-fi writers have even the most rudimentary grasp of science and none understand the necessary inter-connections that result in real-world technological developments. Rather, writers simply stare at the surface and then add larger tail-fins. Sci-fi is at its most interesting when it acts as a reducto ad absurdum, taking current trends to extreme conclusions in order to hold up a distorting mirror to the present. But as a source of reliable predictions about actual future outcomes or technologies, sci-fi is best regarded as a predictor of things that will never, under any circumstances, become reality.