In learning about scenario planning, it seems that the purpose isn't to predict anything, but instead to open our minds to possible futures and go from there. The simple act of opening our minds in this way will make us better prepared for the reality of an uncertain future.
Oliver Freeman describes SP as "engaging with the uncertainty of the future" and "thinking the unthinkable." Therefore, a person wanting to predict the future in the first place is never going to be satisfied with scenario planning.
The point is to change your way of thinking away from predicting the future (which is impossible anyway) and begin embracing the uncertainty in order to move forward more flexibly and with a more comprehensive view of your own context/organisation.
Freeman, O. (2009). Scenario planning. Retrieved from http://www.business21c.com.au/channels/strategytube/posts/2009/09/scenario-planning