I'll buy a new xbox in the next few days, but on my old one I've bought all the Destiny 2 DLC's, I'll keep that as long as I log in to my new xbox with my xbox account (I've bought every DLC with this account) ? Unfortunately, not so experience with technology kram.
Purchased and redeemed content is stored on your profile and will keep you on a new Xbox.
Your scores are also secured by this.