You don't "lose" any characters. Like they stated before - you can only access a single set of characters from a single platform at once with cross save. So if you want Xbox characters, all your other platforms characters or unusable while cross save is active. (But Xbox characters are then playable on PS4, pc, and Xbox) If you turn OFF cross save all characters are available again ( but only on their own platforms, until you reenable cross save - which is then KICKED OUT for 90 days after turning it off.)