Product managers with vision are able to paint an image of what the future can hold without it having taken place yet. They are able to put a dot on the horizon so everyone knows where they are headed.
The best thing that can happen to your team is when they know exactly where they are going and what is expected from them to get there. The worst thing that can happen is when this destination keeps shifting. A strong vision is a long term image of the future. It provides focus, helps us to avoid hurdles, and keeps us going. Vision alone however will not cut it, product managers need to beagle to communicate their vision clearly.