I have on a numbder of occasions argued that this threat can be ignored as the situation is different and Gold is held all over the world. Also, the Gold Standard does'nt apply and so that threat to Fiat money does'nt exist.
How much Gold was turned in when Roosevelt demanded it? Apparently not as much as he had hoped:
The Confiscation Threat
By James Turk
http://www.fgmr.com/confiscation.htm