In his book, The Art of the Long View,
Peter Swartz discounts
Vision as a nebulous unmeasurable thing and that
Scenarios are the answer for predicting the future.
He is right: Vision is a nebulous unmeasurable thing. However, the purpose of vision is not to predict the future, but rather to created a rallying point of what the team plans to be in the future: how the team plans to act, who they plan to interact with, and what change they intend to accomplish.
Scenario building is a tool that can be used to create a picture of what the environment of the future will be. Peter describes that when deciding on a course of action, teams should select plans that are destined to be successful, no matter which version of the scenarios ends up being the truth. The same holds true for creating a vision. If the team creates a vision that will hold true, no matter how the future turns out, then they have created an environment for flexibility and the ability to innovate for those willing to try.
Plans never hold true through their course of execution. Through a good vision the team has on-the-spot guidance so that it is enabled to take decisive action as the environment changes. As long as a team's actions reflect their vision, then they are one the right track.
Scenarios predict the future, Visions create the future.