Metadata can already get send within transactions. There is already a realization in place: https://nut.link/
Emurgo and Ergo already have Oracles in place for Sigma Protocols and in use with their SigUSD stalbe-coin. But those are just in control of manually elected trusted individuals. I would be very surprised if Cardano wants to use their current implementation. Theoretically some way more elegant model could get realized by making every stakepool a potential Oracle provider as we already trust them and they do not like to loose credibility anyway.