FIDO alliance are going to support single credential enrollment

Fido alliance are going to support single credential enrollment that would allow signing in to multiple service providers

https://sdtimes.com/security/apple-google-and-microsoft-commit-to-expanding-their-support-for-fido-alliance/

Seems to me that it has to be based on standard x509 certificates, probably the WebAuthn would adopt certificate enrollment and maybe even renewal

Fido 2.1 already supports large-blob array, so it should quite simple to add