IF, and I do mean IF, they ever put out a box set, they should make it for the true fans like AC/DC did; that is, not an extended greatest hits package that most fans already have, or even a "B-sides" package that most of the hardcore fans have already tracked down, but a real rarities package that can't be obtained anywhere else.
But until the Sanctuary contract finishes and they find a label that might actually promote them, it will never happen, because unfortunately there hasn't been enough demand to buy a $15 CD never mind a $60 box set.