They are definitely hardcoded in many places (e.g. embedded systems, early bring-up - udev style stuff is used for most things these days, but the core /dev/zer

They are definitely hardcoded in many places (e.g. embedded systems, early bring-up - udev style stuff is used for most things these days, but the core /dev/zero, /dev/null, /dev/console stuff is hardcoded everywhere). This would be a kernel-userspace ABI break, which is a big no-no. You could add a new major that does this (keeping the old numbers for compatibility), but I think you'd have a hard time convincing people that this is a worthwhile enough idea; hard-coded new major numbers are in short supply.