The first DDR5 modules will be aimed at the server market, with consumer variants expected to hit the market in late 2021. Initial frequencies will be limited to 4,800 MHz, but, as the technology matures, frequencies will be hitting 6,400 MHz and even 8,400 MHz, while densities could reach 64 GB per single DIMM.
https://www.notebookcheck.net/SK-Hynix-16-Gb-DDR5-RAM-modules-will-enter-production-this-year-4-800-8-400-MHz-expected-frequency-range.459816.0.html