Microsoft is apparently developing a type of “Career” system for your Xbox Live Avatar that could include experience points and possibly even loot crates containing cosmetic items. This report comes from Jez Corden at Windows Central who has seen documentation for this new system.
This new system is partly intended to address a shortcoming in the current Xbox Live achievement system. The total gamerscore does not provide an accurate representation of a player who spends significant amount of time on a small number of games. Gamers who play fighting games at tournaments such as EVO would be one example of this type of player who devotes thousands of hours to their preferred game which are not represented within their achievements.
The career system is said to offer levels through experience points, prestiges and possibly even cosmetic rewards for reaching certain accomplishments; these items could be delivered through a loot crate system. The cosmetic items earned through loot crates can then be used with an Xbox Live avatar. Corden notes that he did not see anything to suggest these loot crates could be purchased but that may be an option nonetheless.
There is a new domain associated with the career system, Careers.XboxLive.com, though the URL does not yet lead to a publicly accessible website. You will presumably be able to track your career through this website.
The career system is not intended to replace achievements. In fact, your achievements will be incorporated into careers. Experience points will be earned through your gameplay activities.
The avatars themselves haave been updated with more customization possibilities and increased detail. Check out this video from E3 2017 to see them in action.