According to a report, both Xiaomi Mi 9 and Mi Mix 4 will have a triple camera setup and will be powered by Qualcomm Snapdragon 855.
The report also states that one of the threee cameras on Mi Mix 4 will have periscopre lens.
Some other brands have already moved from double camera to triple and even quadruple camera setup, but Xiaomi has so far kept a two-camera setup even in the new flagship Mi Mix 3.

Xiaomi 9 is expected to launch in mid-2019 while Mi Mix 4 is expected to be launched towards
Both phones are expected to have 5g but as of now, details of specifications are not know.