All testnet data will be backed up for the future if we decide to keep an active testnet running for developer reasons like testing new code and so on but as for the coins, they will have no value/swap value to the mainnet coins. The testnet coins are not meant for value, purely testing only.

So for the answer, all the coins mined are on a different network than the mainnet network and therefore cannot interact or be swapped for.

It is unlikley that the testnet network will be active again but we have backed everything up in case we wish to reactivate that chain or look back on it for information.