"$USD to zero"... won't be any time soon, but will weaken hugely... to the point of being [nearly] Monopoly Money. The WIPEOUT of the $USD could take 50 years. However, it could lose 75% of its current value quickly from here. That wouldn't make the $USD "worthless", but would be damaging enough to crush the retirement hopes of the Boomers, and more.
Why? Because the US government is too ARROGANT, COWARDLY, SELF-SERVING, GREEDY AND STUPID TO DO ANYTHING ELSE.