I think it will still be fiat but do away with paper and coins and everything done electronically like paying over the net, cards, mobile phone chips, implant chip, etc. That way everything can be monitored that way and easier to collect taxes. I don't believe we will have a fully digital currency like bitcoin to replace current way. If there is some kind of reset, there might be a new worldwide currency put in place (who knows what it will be backed by, gold, commodities, basket of currencies) but we will still have AUD but it will still have a floating exchange rate against the new WW(reserve)currency.
I will still be keeping my metals in that event, will only be a matter of time before it goes balls up, not in my lifetime though.
Keep all options on the table and have a plan for it, as a poster mentioned above it's not wise to become fixated on one possibility no matter what you hear. The current situation can last another 20 years or more, no matter what KWN, zerohedge, etc say.
If/when the US dollar does lose reserve status, I guess that means it is losing value, does that mean every currency in the world loses value? Gold would be a must for US citizens but for everyone else, who knows. We may also see massive deflation, not inflation, during this event so maybe in say Australia it might be worthwhile to have PMs but cash could be king.
I or nobody else knows, only time will tell. Keep your finger on the pulse and you should be fine.
