https://www.techradar.com/news/xiaomi-mi-8-could-land-with-in-display-scanner-on-may-31

Recently we saw video evidence that a phone believed to be the Xiaomi Mi 8 had an in-display fingerprint scanner, and now we know that the Mi 8 will be announced on May 31.

Xiaomi has posted the date on Twitter and there’s no uncertainty about which phone it’s for, as the Mi 8 is mentioned by name.