Migration through the system will allow users to retain their gamerscore, those hard-earned Achievements, Microsoft Points, remaining time on their Gold membership and their profile. What won't move is access to region specific apps, subscriptions and some content that is blocked in the other location due to "legal obligations or regional restrictions."
Microsoft notes: "Before you change your region, make sure you've downloaded any purchased content you want to keep, like movies or music. Content purchases aren't refundable." Switching between regions can only be done once every three months.
Microsoft Xbox One