The first DDR5 memory modules are slated for a 2019 commercial release, while JEDEC will finalize the specifications this summer. The DDR5-4400 module demoed by Cadence requires lower voltages and is considerably faster than the current DDR4-3200 standard, even with CL42 latencies. Later on, speeds will be upped to 6400 MT/s and capacities should reach up to 32 Gb per chip.
https://www.notebookcheck.net/DDR5-4400-RAM-modeules-demoed-by-Cadence-and-Micron-DDR5-6400-coming-soon.301944.0.html