Unfortunately it won't happen, it is completely possible to do, and other games have done it on the psn, final fantasy a realm reborn does it, ps3, ps4 and pc all engage in pve and pvp without any rendering issue which leads me to conclude that bungie don't actually know how to make cross generation work properly. It has nothing to do with the platform, I'm sure if square worked with xbox in the same way they could get cross gen to work fine.