Unfortunately, the Japanese are a proud people. They've said it won't happen, so to then introduce it would be to go back on their word, which would probably shame them and their family, or something.

I can't see it ever happening, much to my disappointment.

Only likely thing that might come out of this, is with enough people shouting for it to happen, the new 'dungeon crawler' event might actually implement this system. I do personally like the 'personal treasure chest' option, as it means that noone can ninja lot you or anything, but the lack of an option to add your loot to spoils if you don't want/already have it is just ridiculous.
It's not that, just that the current system is a huge time sink on cheaply made content (pretty much like kings). The longer we waste doing voidwatch over and over and over and over the less they have to worry about pumping out new content.