The official AMD Ryzen Twitter account has just confirmed that Ryzen 7 will work with high-speed memory.
AMD Ryzen 7 with DDR4 3400 MHz
The debate whether AMD Ryzen works with high-speed DDR memory will not end till we see actual reviews, but there is enough evidence to be confident that there should be no problem using such modules.
AMD has confirmed that Ryzen 7 1700 will work with DDR4-3400 memory with the timings of 18-17-17-37-1T. The most high-end motherboard from ASUS was used for this demonstration (Crosshair VI Hero).
It’s worth adding that two modules of G.Skill memory were used (both 8GB) in dual-channel. So far there is no information how the use of four slots would affect the performance, but motherboards manuals may suggest that for best performance only two slots should be occupied.