Future related (more like, future mentioning) books have taken giant steps back since the beginning of the millennium. According to the data, “future books” peaked around the year 2000. The latest data available, 2008, demonstrates that the level of future mentioning books is back to where it was in the 1970s era. Could it be that there was structural change after the tech-wreck bubble (2001 recession) or even slightly before that period in anticipation of the crash?
Boucher speculates that "our current technological prowess may distract us from the future," and that "technology is a detriment to forward-looking thinkers." My own suspicion is that the peak around 2000 is an artifact of Y2K, and that use of the term is not going to continue to slide but will stabilize before too long.