Anyway, I understand, freebsd-update does not work on the raspberry. Does that mean you cannot update to the next major release, or that you won't get system patches on the raspberry? What about security fixes?
ARM/ARM64 are both still a Tier 2 architecture. There's work being done to get them to a Tier 1 status but it's not finished yet.
In the meantime you can do a source update/upgrade to keep it updated. All architectures use the exact same source tree. So a security patch for i386/AMD64 for example is done in the exact same source code. Whether or not that patch also fixes the issue on ARM/ARM64 remains to be seen but usually a bug for one architecture also applies to another (although in some cases bugs are specific to a certain architecture).