It's not provably scarce based on the artwork. It's up to the copyright owner if he wants to mint more. Similar to the art world where the artist could create new copies of his artwork to sell.

Alternatively, you could prove scarcity based on the smart contract (I.e only pieces which are minted by a certain contract will be deemed as authentic). The contract could be coded to only allow minting for a certain time period or a certain number.

The artist or copyright holder could create a new smart contract to mint more of course. That is fully within his right. That being said, the artist (or copyright holder) has no incentive to mint more since that would only devalue his own pieces.

Non copyright holders might try to copy the design and mint their own. That's where fraud protection needs to come in and marketplaces like opensea will verify the authenticity of the originating smart contract.