I believe eventually we will be transacting in many different forms of Ecash through some sort of fedimint like solution or other layer 3s. People or Nation states may try to issue currency but it will only have value to the extent it is backed by BTC.

Sats are the standard

Final settlement will be in bitcoin(satoshis). 'Local currency' will just become a multiple/fraction of sats/btc to help the locals price in their own unit of account.