One technical problem with this technology is purely optical. All of these approaches only create an object visible to the user via adding light to the background scene.
This is why Hololens demos are made in darkened rooms. Its also even why Magic Leap’s marvellous sounding lightfield technology will be only able to add light to what is already in the scene. There is no ‘black’ in mixed reality, just more light added to what is there. As a result, the virtual objects will always be transparent or brighter than the objects in the scene.
No doubt a solution will be found to this in coming decades, perhaps by using some clever way to exploit the refractory period following a retinal neuron firing, and avoiding the effect of micro-nystagmus, but its a long way off. This means that the sense of a consensual ‘hallucination’ and reality is decades rather than years away.
Which I’m rather glad about as humans appear to believe all sorts of falsehoods even without the reality-bending potential of MR adding to the realism of fake information in our cultural environment.