[cbovis]

The NFTs will still exist and be tradeable outside of OpenSea even if OpenSea itself disappears because they live within a smart contract.

[tpxl]

They will point to nothing and hence (hopefully) be worthless

[testesttest]

Yep, exactly. Opensea hosts most of their minted NFTs on HTTP.

[testesttest]

Open seas contract code is not open AFAIK (binary is obviously available but I have not seen source other than decompile) Many contracts can be updated by leveraging proxy contracts. They can delete your nft if you mint with their contact.