Lay speculation here:

If the first run is on a 28nm process, does this suggest the second generation on e.g. Intel's 14nm process might yield a drastically more powerful HoloLens model in the current form factor, or at least a more compact one capable of all the same (assuming the optics were also compacted) for revision 2?

There's a whole ton of stuff I'm not taking into account such as the physical size of the current HPU, but my guess is that this is the largest point of improvement just going by the process alone.