"It will debut as an Ultegra-level component in the form of the new Ultegra grade R785 Di2/hydraulic disc brake" reports Molly of CXmagazine.com
Shimano says, "Two of Shimano's marquee component technologies have combined to set the new standard in high performance road and cyclocross hydraulic disc brake and shifting systems." Their new R785 series Di2/hydraulic disc brake system will, "provide powerful, dependable performance that is tuneable for a variety of cycling uses and conditions.
The new system will utilize Shimano Di2 electronic shifting, and ICE Technologies hydraulic disc heat management system radiate out heat by up to 200 degrees via an integration of aluminum materials in disc brake rotors and pads. This ensures consistent, dependable braking performance regardless of conditions.
See Another Shimano Upgrade (11-speed drivetrain) HERE
Shimano says that mud will be no problem because the, "braking power is consistent no matter what the conditions or the descent. For cyclocross, racers can brake later in the corners, with more power and better modulation in all conditions.
Molly from Cxmagazine.com also provided a nice list of the weights for this R785 Hydraulic Brake system:
1. ST-R785 STI Shifters / Brake Levers: 515 grams
2. BR-R785 Hydraulic Disc BRakes: 263 grams
3. Brake Hose (BH59) 61.5 grams
4. Mineral Oil: 21.5 grams
5. RT99 Ice Rotor (140mm): 205 grams
Total system: 1066 grams