There is no native export-to-video feature. Much of the joy of using Photosynth is the ability for the viewer to look at what they please in the order that they wish - in other words, the interactivity. Recording a video of a photosynth or a panorama removes this interactive nature, so I am not clear why this is a desirable feature.
If you wish to record a video of a synth or a pano, though, there is certainly nothing to stop one from doing so. Here is a topic where I explain how to use Microsoft Expression Encoder to screen capture a tour of your synth or pano: