> Something needs to happen to break it free, but what that is, I don’t know. It has to take advantage of the form factor in a way that cannot be replicated on the smartphone, and do it better than a small, ultra-light laptop.
This is where "perceptual computing" and in particular 3D sensing comes in. Both smartphones (too small for a decent sensor, battery life and screen issues) and laptops (too bulky to handle) have sub-optimal form factors for this but tablets are perfect.
Take a look at Google Tango [1] for instance or -- shameless plug -- my own company DotProduct [2]. We have been doing this for a while and have tried many different platforms for 3D capture and what we found is that tablets just feel by far the most natural in this environment.
[1] https://www.google.com/atap/project-tango/
[2] http://dotproduct3d.com/