
Improved battery life is a thing if you use a WTF transmitter. I find myself turning wifi on and off a lot when the battery starts to run down. Built in wifi for a hotspot in your pocket is also good - those sticky out transmitters catch on straps and hit things in a bag or, worse, come off and get lost in the gutter.
I imagine a lot of the technologies such as eye-AF and better sensor tech are transferable between DSLR & mirrorless so why not just import the improvements between the two formats and offer a better 1 series DSLR if they can? The mk2 is already a brilliant camera. Even if not a strong enough proposition to motivate you to upgrade, it'd make the idea of a 1 series stronger to new buyers replacing or buying anew and Canon have most of the 1DX tooling in place anyway.
There are some weird omissions on the 1DX2 which I hope they address:

Touch screen operation a la 5D4 - make it switchable in the menu.

Offer the same cropping options of 5D4 (more flexible ratios available) and offer greater placement and sizing fidelity.

In-camera image rotation in 0.1 degree increments - use the scroll wheel to impliment, would be very usable.