Glen Alleman had a recent quote at his blog, Herding Cats, from the renowned theoretical physicist Niels Bohr: "Prediction is difficult--especially the future"
Sometime earlier, Chinese philosopher Lau Tzu is credited with another insight:
"Those who have knowledge, don't predict. Those who predict, don't have knowledge.”
And, from a source unknown, the widely quoted: "If you have to predict, predict often!"
All to say: the future is not always a deduction from the past. Indeed, the past may give no clue at all. Beware any prediction that is calculated. We tend to predict about things we are familiar with, and worse: we tend to predict the things that are suggested to us!