The publication of the JEDEC specifications is paving the way for the accelerated adoption of the DDR5 standard. First to benefit from the new standard are the server and HPC sectors, while the consumer market may first see DDR5-ready systems in 2021. Initial speeds start at 4.8 GHz, but should hit 6.4 GHz in a few years, and capacities should gradually rise to 48-64 GB per DIMM, with a maximum of 1 TB in the foreseeable future.
https://www.notebookcheck.net/JEDEC-finally-publishes-DDR5-standard-specs-Intel-and-AMD-may-offer-consumer-support-by-2021.481350.0.html