The social sciences are sciences; AI predictions are mainly speculative thinking by people who just put on their thinking caps and think really really hard about the future (see some of the examples in http://lesswrong.com/lw/e79/ai_timeline_prediction_data/).
Are you saying that these predictions are unscientific because they are based on untestable models? Or because the models are testable for "small" predictions, but the AI predictions based on them are wild extrapolations beyond the models' validity?
An over-simplification, but an evocative one: