I still can't buy the upgrade I'm a Legacy owner of TTK Collector's edition, and yet I can't purchase the Collection upgrade for xbox one. The purchase button is nowhere to be seen on the xbox store, and on the microsoft store it shows unavailable. I've attempted three times to resolve this issue with microsoft tech support to no avail. Everytime I've had to explain this whole confusing mess to them and they always say that there is nothing they can do and that they'll "let bungie know", or "this is a known issue that we are working on." To declare that this problem is fixed is just not true.
Fixed for me, I just had to redownload the taken king on legacy console. This whole ordeal was frustrating.