This could be a great feature for Macro, giving you functionality similar to Lytro.
"The 5D Mark IV also has some new tricks up its sleeve including Dual Pixel Raw, a nifty option that can prove useful in specific shooting scenarios. It works by recording two 30MP images, one from each of the 'left-looking' and 'right-looking' photodiodes at each pixel. Previous Canons have combined these two signals at each pixel, but Dual Pixel Raw gives you the option of keeping them separate. This results in a file that's twice as large, but one that allows for 'image micro-adjustment,' 'bokeh shift' and ghosting reduction"