First of all I doubt that a revolution could ever happen short of the federal government declaring that future elections are unnecessary and will no longer be held. Even the inevitable national declaration of bankruptcy will not be enough to trigger revolution, only the election of a national strongman.
A far more likely possibility (probability?) is the secession of several states, perhaps even the majority of states. There is already (as reported by Glen Beck) an active, if small, secessionist movement operating in all 50 states. This is a possibility because the vast majority of federal troops could no longer be persuaded to open fire on Americans. Federal law enforcement absolutely, the vast majority of the army and marine corps no way. And if pressed to do so there is a good chance that many would simply change sides bringing their arms and equipment with them. Many things could trigger such a movement including gun bans, a defacto ban on opposition media, the growing domination of all 50 states by a handful of states, and/or a national economic collapse.
Proud Life Member: National Rifle Association, California Rifle & Pistol Association, and the Second Amendment Foundation.
Annual Member: Revolutionary War Veterans Association (Project Appleseed) and the Madison Society.