It seems like the Xiaomi Mi 7 will ship with an in-display fingerprint scanner, as it seems like the company's CEO just confirmed this functionality. Lei Jun, Xiaomi's CEO, mentioned this in a comment on Weibo (Chinese social network), while he was responding to a random user's comment posted in the comment section. Do keep in mind that both the user and Lei Jun used Chinese in order to communicate, so the translation may not be spot on, but it seems like the user suggested that the Mi 7 may not have an in-display fingerprint scanner, after which Mr. Jun confirmed otherwise.
The Xiaomi Mi 7 was actually expected to arrive in the first half of this year, but at the moment, it seems like it will be announced in H2 2018, mainly because the Xiaomi Mi MIX 2S arrived quite recently. The Xiaomi Mi MIX 2S is the company's new flagship, it is fueled by the Snapdragon 845, made out of ceramic, and it comes in both 6GB and 8GB RAM variants. It's quite probable that Xiaomi will not introduce yet another flagship-grade phone that soon after the Mi MIX 2S arrived, so the Mi 7 may arrive at the end of summer, though that's just a wild guess. Only a couple of smartphones have an in-display fingerprint scanner at the moment, like the Vivo X20 Plus UD, for example. That handset comes with Synaptics' Clear ID fingerprint scanner, which is a bit slower than your regular capacitive sensor, and it is only compatible with OLED panel.s
The Xiaomi Mi 7 is not only expected to ship with the Snapdragon 845 SoC, but it will also pack in other flagship-grade specs, and chances are it will be noticeably smaller than the Mi MIX 2S. The Xiaomi Mi 7 is expected to ship with considerably thinner bezels compared to the Mi 6, which probably means it will sport a larger display than its predecessor. It is still unknown whether the device will sport a display notch or not, though the alleged Mi 7 did leak quite recently, with a display notch, but who knows if that leak is legit or not. In any case, new Xiaomi Mi 7 info is expected to surface in the near future, so stay tuned for that.