Major we'll-see risk factors I identify:
1) $3,500 is expensive, any way you slice it. That makes it price-competitive with a workstation.
2) The stand-up-and-work environment they demo'd doesn't work for a lot of people. But if you sit down, you lose a lot of the benefit of that panoramic space.
3) Their gesture interface has to be rock-solid (meaning no false negatives but also no false positives) for it to be part of a daily work environment.
4) We've been experimenting with headsets for long enough to know that for the average user, the amount of time you can comfortably use one is lower than the amount of time seated at a mouse-keyboard-monitor UI.
5) The battery life is 2 hours, which is like nothing. You can use it plugged in, but then you're plugged in (meaning not only that you're tethered to somewhere, but that you've got the constant pressure of the tether disrupting your head motions, which adds up over time in irritation).
All of that having been said, if anyone has a prayer of overcoming these obstacles it's Apple. They've got the software / hardware / UI / UX integration in-house to take a solid run at the challenge.