Dell XPS 15 9550 and Dual Dell 4K P2815Q Monitor Hookup Question

I am picking up the XPS 15 this week and currently have two P2815Q monitors I am using with the Microsoft Surface Book.  Currently these are connected to the Surface Book via a single mini-display port cable with the 2rd 4K connected to the first via mini-display port.

So my question is how do I connect these monitors to the XPS 15.  I understand the XPS has Thunderbolt and a single HDMI 1.4 port.  While HDMI 1.4 is not capable of driving 4K at 60hz, I'm also wondering what the new Dell Dock is going to bring to the game here.

Would love some help, so thanks in advance. :emotion-1: