Earlier quoted context omitted.
Foveated rendering only became relevant when Nvidia recently started supporting Multi-Resolution Shading. As new techniques and tools like this get better support we can be a lot more efficient with lower powered hardware. It was interesting to hear Carmack last year talk about re-introducing interlacing as a way to reduce latency. Although, I'm just reinforcing what you're saying =)
Huh, interlacing is a neat idea to reduce latency, but I'm guessing you'd want a form of intra-frame temporal anti-aliasing, otherwise it might look pretty fugly. Whether or not this would neutralise any latency advantage due to the computational overhead of doing this, I'm not sure...
For VR, the consensus I've seen seem to push for multi-sample AA > full-screen AA > temporal AA (I feel like I've even seen no AA is better than temporal AA). I'm not quite sure if it's performance, architecture (they really prefer forward renderers instead of deferred renderers for low latency), or aesthetics. In the little bit I've done, when just playing with knobs temporal AA looks better to me. Without AA specular highlights are way too distracting and pop too much.
This reference[2] talks about the extra velocity buffer needed for temporal AA and the fact it tends to over-blur which can fuzz out fine details (low resolution is a touchy subject in VR).
There's a lot of moving pieces when making decisions. In talking about interlacing, he was ideally talking about not having to create a whole image buffer before sending data to the hardware--just rendering parts (well, scanline) of the image that moved.
[1] https://youtu.be/gn8m5d74fk8?t=10m54s [2] https://www.youtube.com/watch?v=Xk3WUk5T2TQ&feature=youtu.be...