if use usb ; then
doins etc/openct.usermap || die
newexe etc/openct_usb openct || die
Well, that won't do anything useful without hotplug; in fact it won't do anything useful even with hotplug installed on udev systems, so USE=usb is a wrong check. I'd suggest to just completely drop this, the ebuild already installs udev rules and scripts anyway.
Is that policy to drop hotplug stuff from Gentoo?
Is udev will be a requirement for future layouts?
Hmmm, I don't really understand what you are asking here? udev is required unless you maintain static /dev... plus USE="usb" tells us exactly zero about whether the user actually has udev installed or not. The /etc/hotplug stuff is completely useless on any udev system.
If I understand correctly, there is an old preudev hotplug configuration... There are a lot of packages with usb USE flag that use it, one comes to mind libgphoto2... Are you sure nobody uses this interface?
media-libs/libgphoto2 doesn't install any such stuff. The only two ebuilds that install anything to /etc/hotplug are this one and sci-geosciences/gpsd (Bug 210079). It will be completely unused on any udev-based system - udev doesn't use hotplug since 096 or so...
OK. Removed hotplug stuff.
Do you use this package?