Manage ongoing development. When one of the triggers occurs, react to it as shown. Development managed over time, so User can continue to maximize value given what's learned during development. User picks one iteration worth of stories from release plan. Programmer implements them.
Programmer realizes velocity is wrong.
Programmer re-estimates velocity. User identifies new, more valuable story. Programmer estimates story. User can remove estimated points from incomplete part of existing plan, and insert the new story. Programmer re-estimates velocity and all stories.