The motherboard also comes equipped with three M.2 slots for storage devices, with one marked as a PCIe 4.0 x4 connection capable of 32 Gb/s of throughput, while two SATA M.2 slots run at the same speed. Biostar's listing indicates all three of the M.2 sockets hang off the platform controller hub (PCH).
Those suggested memory overclocks are promising. Seems like Zen 2's memory controller will be capable of hitting much higher speeds, if the previously-conservative numbers by the manufacturer have been boosted that much. With that being said, we'll have to see how well Zen 2 and the new revision of IF scale. Current Zen starts getting diminishing returns around 3000. If it scales well to at least 3600 I would be happy, since 3600 kits are starting to get pretty affordable now.
Storage devices will be PCIe 4.0 compatible soon. In the not so distant future, high end M.2 devices won't have a problem taking advantage of the extra bandwidth, seeing as how M.2 is limited to 4 lanes.
Also, it's future proofing to some extent. If you buy a 3.0 platform today, you're stuck at 3.0 speeds. If you buy a 4.0 platform, both 4.0 and upcoming 5.0 devices will operate at 4.0 speeds. There's no good reason for AMD to skip PCIe 4.0 right now, it benefits their server business almost immediately, and will aid consumer platforms to some degree in the near future.