Android's navigation buttons are almost the perfect example of what user interfaces should be. They should be near invisible to the user's mind, not requiring conscious thought to use. They really only get noticed when things break or change. The latter will seem to be the case according to a recent insider tip. According to the source, Google will be introducing visual changes to the navigation bar icons that will go beyond just subtle aesthetic tweaks. It could, however, also be a prefiguring of behavior changes.