When you were a small child you learned about object permanence: Even when you are not looking at an object, it continues to exist. If you put your teddy bear on a particular shelf in your closet before you leave for school, it will still be there when you return.
When we are all wearing mixed reality glasses (or contact lenses or implants) object permanence for many things won’t be a necessity. More and more of the “built world” we see around us will be virtual constructs, unconstrained by the laws of physics and inertia.
Yet we may choose to impose a virtual object permanence anyway. When we place a virtual object in a particular place in the physical world, we might wish to impose constraints upon that object’s behavior, so that it stays where we have put it.
To me the question of how much — or even whether — we will do this, in the long run, is quite deep. It comes down to the following question: Is object permanence an intrinsic feature of our biological human brain, or is it simply an adaptation that our brain makes in childhood in response to encountering the physical world?
If the latter case is true, that increases the possibilities for a mixed reality future. If object permanence is not an intrinsic feature of our human brain, we may end up evolving as a social species to replace it with something far more fluid and flexible.
Of course children will still want to find their teddy bear when they get home from school. But in the future, maybe they will just Google it.