ah, now it's revealed! gpgpu for pseye! sure... but could happen, of course. would still be worse than dedicated hardware, though (and worse than fpga, that is).
More resource intensive. But not necessarily 'worse', quality wise, than a hardware implementation.
Stereo reconstructed depth maps are noisier than ToF data, but is it 'good enough' for 'good enough' skeletal tracking?
SoftKinetic's library is based on depth maps, so I presume they are doing the requisite stereo reconstruction on PS4 in a performance envelope that we can surmise is - at least - acceptable for a game like Just Dance 4.