What do you mean? They're critical to making the physical version of DL work. They could be supplanted in VR of course but I don't see how you make an IRL DL without them.

What if eInk paper was as cheap as paper and each sheet had a small processor and could mesh network? What if computing was so cheap you could toss it out when you were done with it like a Kleenex (not a big stretch - an electronic toothbrush has a 3 cent chip which has more computing power than what the Apollo moon shuttle had onboard). Bret is thinking in decades, not years.