Looking at history, they'll just take it for themselves. Does anyone remember when US government seized BTC-e exchange, where BTC-e user never get their BTC back?
You are right, there have been no such time when any government gave the seized funds back, but what if they tag these BTC as recovered BTC not seized so maybe they pass some bill where whoever recovered those BTC are responsible for giving them back to the rightful owner? Well, if that happens, then we might see thousands of people declaring themselves the Satoshi.
Or maybe if Satoshi also upgrades its wallet security by moving funds to QCs resistance wallet.