I think the advantage of having a model update in an .ipn file is being wasted by breaking the "link" from assembly to .ipn when the presentation gets exported to a .avi or .wmv file. If a .ipn viewer was available, it would allow people to view the most up-to-date version of an assembly in a presentation-style format.
Also, if annotations were available in the .ipn environment; why would anyone go outside of Autodesk viewers to view presentations?