Can someone reassure me that the US-import versions of the various 5GHz RouterBoards are limited via firmware, rather than via hardware?

In other words, the next time the FCC rules change, will a firmware update be able to re-enable previously restricted frequencies on these devices? Or are the radios themselves physically "crippled" to prevent them from ever using the frequencies that are prohibited under today's rules?

I hope it's the former, but I wouldn't put it past the FCC to insist that no firmware change (or hack) could possibly enable non-compliance.

Mikrotik stated that it is a bit more than just using the lockpack. Hard to guess, my unconfirmed tip is that the software behaves differently according the model name, so it could be expectable that in case the regulation changes in US, newer ros version might be able to reflect that. To be sure, ask support via email and keep us informed about the answer.