Strategy Analytics Emerging Device Technologies has just released a new report describing the relationship between sub-6GHz and mmWave smartphones.
Currently commercial mmWave networks are available only in United States but Strategy Analytics estimates there will be more networks around the world in the future.

The mmWave support will grow to be in approximately 27% of the 5G smartphones by 2024.
Our clients can access the report and data through this link:
Global 5G Smartphone by Technology Forecast to 2024