We could also bring up the sensor in the 1DX. It's only 18 mp .
Same, four-year old, 18mp sensor = big disappointment !
New, 18mp sensor with better DR and 1+ stops better ISO = hurray!!!
P.S. It's not the number of megapixels that will disappoint but their quality.
Bring 1DX quality to 1.6x sensors and nobody will complain that 18mp is not enough.
(Yes, I know that this is difficult/impossible. Just giving an example here.)