I think that the object permanence of apps will be one of the “idioms” of spatial computing that ends up being the thing that just makes sense and we won’t look back from. You can imagine having certain apps strewn about your house, and certain apps scattered around your office, much like you would physical objects. Our minds are used to mapping physical spaces, and I bet after a few generations of this tech we’ll realize this is a more comfortable way to manage our HCI. It might not always be the most efficient, but I think it may become the most intuitive.