They updated their FAQ, not sure exactly what they mean. It's not looking too good IMO
"There are three similar-sounding factors at play here with the MacBook + HydraDock video resolution support topic. One is the maximum resolution supported by the DisplayPort 1.2 standard, which is 4K. Another is the video resolution supported by the USB 3.1 Displayport Alternate Mode standard, which is 2560x1440. Another is the resolution supported by the GPU in the Apple MacBook, which is 3840x2160 over HDMI and 2560x1440 over USB 3.1 DisplayPort Alternate Mode.
There are people arguing on the web that we are confused about the specifications of our own product. We are not. The confusion is that the MacBook does not have a native DisplayPort connector it pipes out video over the USB-C jack using USB 3.1 DisplayPort Alternate Mode.
The DisplayPort v1.2 standard supports 4K video. But, USB 3.1 DisplayPort Alternate Mode v1.2 does not. It only supports 2560x1440 DisplayPort connections. There is an included method for configuring HDMI over Alternate Mode DisplayPort out of the new MacBook that supports either 1920x1080 HDMI video at a 60Hz refresh rate, or 4K (3840x2160) HDMI video at only a 30Hz refresh rate. It is because of this capability of handling a 4K display over HDMI (only) at only a 30Hz refresh rate that Apple has chosen to state in their marketing and specifications for the MacBook that the product supports "4K displays!"
After nearly a year of development and engineering we clearly understand the capabilities of not only USB 3.1 Alternate Mode video, but of our own product. There was a cost-complexity choice we had to make involving one of the video processors in our product that required us to choose whether to support the 30Hz HDMI 4K mode from the MacBook or not. And, we decided to only support the 60Hz refresh rate modes, as this is a desktop computing product and 30Hz flicker is annoying something we think constitutes "barely supporting" 4K video.
So, all that now said, the HydraDock supports one of the following at a time not both: one Mini DisplayPort connection at up to 2560x1440 pixels, 60Hz refresh rate; or, one HDMI connection at up to 1920x1080 pixels, 60Hz refresh rate."
https://www.kickstarter.com/project...port-usb-c-dock-for-apple-macbook/description