Most building codes (as adopted by the AHJs) do not require systems not part of the job to be brought up to current code if they met code at the time of install, are in good repair, and are not being significantly worked on. You can add an addition without converting all the old bedroom breakers to AFCI. (That represents a much higher safety risk than any generator inlet could possibly be.)

Well yeah, but if the addition (or your new EV, which might actually support working as a home backup battery) requires a new panel, then the port would be required.

On the other hand, generators are rapidly becoming obsolete, so this might be akin to requiring installation of upgraded coal shoots.