It's not going to be as big as an upgrade as the 7D II was compared to the original for stills (just like the 1DX II compared to the 1DX), but it will be very solid.
More speed (12 fps?) and faster card support for that, better IQ and AF (more high-precision cross-type points, more points at f/8) and better video features will be the main upgrades.
Maybe it will remain around the 20MP mark with a similar 1.4x crop to the 1DXII (in addition to the 1.6x) for 4k, maybe with 60fps as well (if CFast 2.0 is included), and 1080p at 120fps.
All these video features mean the AA filter is there to stay, nothing wrong with that, really.