Hi,
Thanks for posting!
Apologies for the confusion, I sent a reply to you initially but realized I provided incorrect information, it seems you still received that reply even though I deleted it! 
The Microsoft Surface Pro 3 does indeed support both DP 1.4 and DSC so we expect that you should be able to drive at least one 4K 60Hz display.
The Microsoft Surface Pro 3 does indeed support both DP 1.4 and DSC, however our dock does not support DP 1.4 hosts. Through our TBT3-UDC1 docking station, the Surface Pro 3 supports a single 4K 30Hz display or two 1080p 60Hz screens.
If for some reason you run into issues with this, please do let us know.
Thanks!
Mitchell