For my 'new' (with some older parts, a.o. DDR4 2133) system I'm thinking either Ryzen 7 1700 or a Xeon E5-2620 v4. I'm not a heavy gamer and the system will be running Linux (Calculate/Gentoo) or FreeBSD, so compiling capabilities is a big consideration. The prices are about the same over here. Yes, the Ryzen has a higher clockspeed, but it seems the Xeon is better for virtualization (KVM). Will the 'slow' memory hold the Ryzan back?
For the mb, I'm thinking of the ASRock X99M Extreme4.
The Xeon board is more expensive than the AM4 one. There is not much choice in 2011-3 that is uATX it seems. Another choice would be 1151 with a Xeon, but these are only 4-core, but there is a lot more choice in mb.
Waiting is not really an option, and beside if something new is announced there, how long will it take to get to market? Beside, on *nix, it's not always a good idea to have the latest and greatest
I have heard while memory speed doesn't matter with Intel, it does with Ryzen, personal if there isn't a huge difference in the price of both builds I would go with Intel. The biggest advantage Ryzen has over Intel is more bag for the buck usually.
If your workloads are aimed to run multiple vrm´s and utilizing pci-e passtrough. Then intel might be the better option at this moment. Because iommu groupings on current Ryzen X370 boards are a mess atm. Atleast from what i have read sofar, not manny seem to be that succesfull with pci-e passtrough for gpu´s on Ryzen yet.