NFT Interoperability

I have a general question about NFT’s and their interoperability. Is anyone working on a project or something that is aiming to accomplish this? I know Polkadot is working on blockchain interoperability, maybe this will be the solution to that? But I’m generally curious, say ETH loses popularity, would the ethereum based NFT’s start losing value? Would be cool if you can transfer and validate between different blockchains