Go with Jim Rickards estimate as its far more conservative but still very high by todays standards. An outright switch to gold is unlikely, we are talking about default in value occurring even while gold rises and obviously dollar likely falls in value with less purchasing power but an advantage to export I guess is one positive to it.
So the main thing I can remember from Rickards talk through is about a 40% backing to gold exchange to any currency standard, that eases the demand for gold that occurs and lowers the price down to 10k or higher. 10k is enough for trade to continue where as presently gold is so low a price it would be unable to describe the trade done but both a higher price and that 40% backing allows a link to exist to a solid value in every trade especially between countries in global commerce. Poor and failing currency is especially a difficulty where it causes a loss of confidence and reduces business done, then its a problem. Right now we hear often how QE is so stimulating to the economy, it'll reverse in sentiment at a point where the value lost is apparent.
Heres Dollar index over 20 business days recently and shows a loss of about 5% of value in that time. Pretty volatile in the big scheme and considering its the global reserve currency.