A sub-$5k 1DCII with full frame 4k and filesizes near the A7sII, and ergonomic/functionality improvements seen with the a7s... Canon would retake the DSLR video throne in an instant. It would kill all the momentum Sony and Panasonic have been making. Say what you will about all of Canon's mistakes in the video game lately, but they still put out arguably the nicest colors and most filmic look between them, Sony, and Panasonic.
The C300II is amazing but outside of the price range for people looking at Sony and Pansonic, but a 1DCII with those specs to me feels like the definitive step up from the 5dm2/5dm3 crowd like myself.