Isn't this exactly the issue addressed by money laundering? Would this not simply force a large number of people into dealing with organisations or individuals who can convert their existing stockpile of (no longer valuable) cash into a smaller pile of cash that still has buying power? A naive approach would be to 'hire' a large number of people to cash in amounts of notes that would be just under the level considered suspect by promising them a cut of the exchanged money. I'm sure there are existing criminal networks that could achieve such schemes (or better thought out ones) within the window of Nov 10 to Dec 30.

No one will be willing to do that work. And its difficult to scale such operations. They may convert some small amount (probably upto 50k), but anytihng more than that, it'll be getting tougher

I wonder how long till the new format is duplicated?

The duplication is a minor concern the major concern is lost income tax revenue due to an underground cash economy. By restricting numbet of 500 and 2000 notes and forcing owner declare assets it put massive pressure on the black money.

The big ticket black money is in swiss accounts,real estate and gold.