Game devs have the ability to update their game differently on different consoles, Bioware did it for DAI, just released the game for last gen, patched its bugs, and all updates and dlc were strictly current gen. Last gen consoles arent holding anyone back. If bungie wanted to, they could do things for current gen and not do them for last gen, like bungie bounties and the thriller dance. The problem is, Bioware didnt promise support for last gen, bungie did. You dont make promises to sell games, then back out on them once you have the money. So in summation, bungie cannot drop support for last gen, and last gen aint holding anything back.