As TechPowerUp points out, the 16Gb chips could be used for dual-ranked 64GB modules, quad-ranked 128GB LRDIMMs and octal-ranked 256GB LRDIMMs. This basically doubles the theoretical maximum memory of server platforms, to up to 4TB RAM in AMD EPYC based systems.
The 16Gb DDR4 dies from SK Hynix are organized in 1Gx16 and 2Gx8 configurations, and supplied in FBGA96 and FBGA78 packages, respectively. SK Hynix offers DR4-2133 CL15 and DDR4-2400 CL7 variants, both require 1.2V. In Q3 2018, SK Hynix plans to add a DDR4-2666 CL19 version to the mix.