Technically yes, but they haven't come out with it. A huge missed opportunity IMO. It could have moved quite a few more 950/950XL units if all Surface Pro dock owners could just plug in their phone and use all hardware already hooked up to that dock.
BTW, I think you have just invented the product name: OneDock. Very MS.
What I'd love to see is a battery powered portable monitor - with no processor in it, just a display and battery - that had a phone dock built into it. One monitor + one USB C cable + continuum phone would be very interesting to me
Yeah, there's really no technical reason why they can't do a unified dock in the future, but for now there's a few core differences:
1) Surface Dock has MANY more port options including audio out and Ethernet, additional USB, and can power 2 4K monitors. It is both sized and weighted to suit a desktop environment.
2) Lumia Dock is smaller and while weighted, it's still designed for both mobile and desktop usage. Since it connects via USB-C and Surface doesn't yet have USB-C, it made little sense to use the same one for now.
That said, tomorrow I'll have both docks in my possession, so I'll be happy to test a bit and see if it's possible to interact with them.