I think the dollar index is a lagging indicator. After people start massive selling, then the dollar index falls.
I'm sure there are some folks out there who watch the dollar index, and might start selling when it hits some trip point, but the kind of massive, unexpected sell-off that John Williams is warning about happens precisely because tens of millions of people who may not even know what the dollar index is decide that holding dollars is a bad idea. Not currency speculators, but small businesses, people who hold US government bonds, people who decide they want more gold, or silver, or oil, or access to food.
I've used this metaphor before, but it still applies:
We are sitting on a large stack of gunpowder kegs. There are fuses running everywhere, in knots and tangles. There are lit torches. We can hear fuses sputtering. We can smell the smoke.
We know exactly what is going to happen, we just don't know when. When it finally does happen, it will be over very quickly.
The way to leave the trap is to get rid of as many of your dollars as possible, converting them into something that won't be blown to smithereens. It's easier said than done, but it is the only escape from the stack of powder kegs.
Peace,
Silver