I understand that, but that's not supported by any current standard as far as I know. We'll need a new TPM standard for this, which probably also means it will take years before every device supports this feature as modern computers can easily last five to seven years if you replace the batteries and don't cheap out. FIDO needs something that works now, or maybe tomorrow.

Agreed, and that's why I say in my original comment that I don't see it happening in the short term. If we had something that worked now or maybe tomorrow and was acceptable, it would simply be virtual authenticators; an authenticator implemented entirely in software. There's no practical reason why password managers like 1Password can't do that beyond attestation which nobody checks anyway. But in the end, I don't see the big three participating in sharing. The threat model changes so much that especially for Microsoft (in cell phones) and Google (in desktops) that means trusting an adversarial OS they have no control over

you can do it easily enough with the current TPM operations (2.0, not 1.2)