Once we permit the FBI to task private companies via court order, there's no way to predict how far that tasking will be permitted to go.
> If the FBI demands that you open a door for them, does that imply you're not allowed to brick up the entrance later on?
The FBI is not demanding that Apple open a door, it is demanding that Apple build a custom software system for them. If the FBI can tell Apple how to build software today, then the FBI can probably tell Apple how to build software tomorrow.