It seems possible that Xiaomi could be working on flagship smartphones for a potential Mi Mix 4 series, or at least devices with the Mi Mix moniker. Scant details have been offered by a well-known leaker on Weibo, however, there is mention of a 120 Hz refresh rate for the display which has often been rumored for a Xiaomi Mi Mix 4.
https://www.notebookcheck.net/New-hope-for-a-Mi-Mix-4-as-details-start-emerging-of-two-upcoming-Xiaomi-flagship-smartphones.464780.0.html