Rock bottom is in most cases (except for death) a false bottom- like quick sand. But I think most people associate rock bottom with their last time that made them stop. But yes, you can keep falling further in most cases until you are 6 feet under. It all depends on if that is your rock bottom that makes you stop- its all relative to the person and situation.
Rock bottom could be an arrest, accident, or just a realization that man life sucks right now--