I would imagine at some point government will start becoming creative to tax the billionaires or the corporations. Though the masses becomes entertainment for the billionaires to keep money valuable else like you said if they all have the money then it's worthless. The government by this point would be so weak since rampant corruption would be so ingrained that any idea of taxing the billionaires would be incredibly hard to pass. So I think what likely will happen is a societal collapse. If this were to happen globally end of our current civilization.