What will happen to peoples money?

Hi, apologies if this question has been asked before but I am wondering what the plans are concerning the destruction of physical and digital money at the point of transition when it is no longer needed? Will all the notes be incinerated or stored away in a vast underground vault somewhere in case of a return to the current system in the future? I guess the coins could be smelted into raw materials etc? Sorry my English is not so good, but these are questions I have been thinking about today..Thanks