Will the "new focus sensor" be usable in live view -- and will a variant of it find a home within a future EOS Rx?
I believe Canon is referring to its iTR sensor here, which is used to aid exposure and subject recognition in view finder mode. In LiveView, this sensor is not necessary because the primary sensor can be used for that. With the EOS R for example, there is no mention of iTR.
With the 1DXII the iTR sensor only has 736 x 496 "Pixel". No idea on what kind of pixels these are, as it is supposed to sense RGB and IR information. Anyway, that's just 0.36 MP, so even if it is increased by a factor of 28 yielding a 10.8 MP sensor, on a mirrorless body you are probably better of using the primary image sensor anyway.
Non the less I guess such a high resolution iTR sensor will allow face and eye detection as well as subject tracking to make great progress, even if the number of AF points remains the same. They write specifically about the resolution being this high in the center. I guess having two high res sensors that cover the whole image is too expensive even for a 1D body?