DisplayPort is a standard for high resolution diplays. DisplayPort 1.4 can support up to 8K resolution at up to 30 hertz on a single cable and 60 hertz over two cables, here showing it off running on an upcoming announced Dell 8K 32" display. DisplayPort can also support HDR or high dynamic range.
If a device has USB type C and the necessary hardware it can output displayport video through Type C. Through USB Type C a device can be charged while outputting video and being connected to a USB hub. Display port alt mode can switch to HDMI for HDMI displays. The Snapdragon 835 has displayport functionality so more devices in the future should have it. Mobile devices in the future could potentially Run multiple display monitors through a dock.
A dock using High Bit Rate 3 (HBR3) over DisplayPort 1.4 can output to multiple 4k monitors.