Rumour has it that the Mi Mix 4 has been sighted on Geekbench, complete with 10 GB of RAM and a Snapdragon 865+ processor. While the Mi Mix 3 is long overdue an upgrade, there is no truth to this latest Mi Mix 4 rumour.
https://www.notebookcheck.net/Do-not-be-fooled-into-believing-this-latest-fake-Mi-Mix-4-leak.462652.0.html