The Mi Mix 4 will reportedly launch next quarter, as Xiaomi looks to release its second Mi Mix handset this year. The Mi Mix 4 will allegedly not come cheap though, and could be even more expensive than the pricey Mi 11 Ultra.
https://www.notebookcheck.net/Fantastical-Xiaomi-Mi-Mix-4-rumour-details-astronomical-price-and-uninspiring-display-specifications.546694.0.html