For physically hardened devices, this attack vector can be mitigated quite efficiently by including an attestation key with each device and validating that after taking possession (or ideally before any interaction). At least one competitor does that.
To my knowledge, current Trezor devices are unfortunately not (sufficiently) key extraction proof, though; in that scenario, attackers might be able to extract the private attestation key of a legitimate device and then go on to impersonate it in their own version.
This again could be mitigated by e.g. making the attestation key device-unique and offering an online validation service (which could keep track of unusual verification patterns and alert users), but it's not an easy problem to solve.
Everyone would know it and the attestation key would be obsolete. New wallets will be made with another key, and for old wallets users already know they are genuine anyway.
Hopefully the attestation (root) key is itself stored in secure hardware (i.e. an HSM or similar) that can't be reprogrammed unilaterally, even by a privileged actor.
To my knowledge, current Trezor devices are unfortunately not (sufficiently) key extraction proof, though; in that scenario, attackers might be able to extract the private attestation key of a legitimate device and then go on to impersonate it in their own version.
This again could be mitigated by e.g. making the attestation key device-unique and offering an online validation service (which could keep track of unusual verification patterns and alert users), but it's not an easy problem to solve.