Could you synchronize two Kinect devices on one clock and then toggle the display/capture of that grid every odd or even 10ms span? So, only one grid is displayed and processed during its 'slice' of time, with the grids strobing rather than continuously projected.

Software-only, or would that result in too jerky of a motion capture?

Absolutely you can. That's exactly how LED matrix displays work (look up charlieplexing).

Unless the 3d environment is rapidly changing, you don't need that many frames per second from each device to capture a good image.

25 fps is one frame every 40ms.

How about slightly different wavelengths of infrared?

10ms seems like a reasonably small period of time. I believe it is considered to be effectively instantaneous in UI.

Edit: Although, I suppose the "refresh rate" of the entire system would then be 20ms, which might be noticeable. Chop that down to 5ms per Kinect, and it might be viable.

Only one "eye" [Kinect] has to notice/process the movement; the other can infer, during the integration step, that the "rest" of a moving object comes with it, rather than stretching out.

Couple this with shutter-glasses and time-multiplexed display. Now you can make a "3d" display that works for multiple viewers.

Of course, the frame-rate would suffer.

How about projecting different patterns?

Here's a nice video, if anyone's curious about what the infrared pattern looks like. http://www.youtube.com/watch?v=nvvQJxgykcU

Last week, a guy from Microsoft Research said that they got multiple cameras in the same space working, but that others in the lab had problems with it. Seems to depend on the setup, but is obviously possible

Maybe you could turn one on, capture the positions of the dots, and then turn the other on, and somehow guess which one was which when the 3d mesh changes (from motion)?