I'm ready for QPAF (Quad Pixel).
HDR plus AF.
it seems like a natural evolution to me
I'm not sure DPAF or a hypothetical evolution to QPAF is really a means to achieving HDR. Remember, ML had to cut resolution in half in order to achieve its makeshift approach, not because they did not have dual pixels...but because they had to use both the per-pixel amps as well as a secondary downstream amp. Doesn't matter how many times you dice up a pixel...if you have to use the downstream amplifier to achieve ML's style of "HDR", then diced pixels won't help.
Additionally, HDR implies 32-bit float data storage. Current camera ADCs are still limited to 14 bits int. Canon already has 12 stops of DR...seems a bit extreme to use such a convoluted approach to improving that by a mere two stops, when their problem actually lies in the ADCs themselves. Canon could take a far simpler approach...increase the parallelism of the ADCs, and move them closer to the pixels, to reduce the amount of noise they introduce into the signal. That's what everyone else is doing, and it is quite effective.
Assuming Canon was able to use QPAF to do some form of HDR...unless they increase the bit depth of the ADC, it isn't really going to be HDR. You would still be limited to 14 stops of DR, albeit achieved via a rather convoluted apprach that could be more costly and less effective than simply modernizing their read pipeline architecture. To get true HDR, Canon would need to use 32-bit ADC, and use floats rather than ints. At the very least, to improve DR by a meaningful degree, they would need to move to 16-bit integer ADC, however that wouldn't necessarily be "HDR".