If a new rumor is to be believed, the Xiaomi Mi 6 will not ship with an ultrasonic fingerprint scanner. This rumor comes from the depths of Weibo (Chinese social network), like many other Chinese smartphone-related rumors do. This particular rumor was shared by @Mocha Socialist Workers page, and that's the same source that reported that the Mi 6 will ship with a flat 5.2-inch fullHD display and Snapdragon 835 SoC, which a rumor that surfaced a couple of days ago..
That being said, Xiaomi had utilized an ultrasonic fingerprint scanner in the past, the Xiaomi Mi 5s shipped with such a sensor. According to the source, Xiaomi will turn to a local (Chinese) manufacturer which will provide a fingerprint scanner for the Xiaomi Mi 6, while the ultrasonic fingerprint scanner that was included in the Mi 5s is manufactured by Qualcomm. The source did not say what kind of a fingerprint scanner are we looking at here, but chances are it will be your regular fingerprint scanner which will be placed either below the phone's display, or on the back of the Mi 6. In addition to all this, the tipster also claims that the Mi 6 will become available in April, and that it will be announced in March, though he did not share any specifics date with the public, unfortunately. This information is probably accurate, as Xiaomi will not attend this year's Mobile World Congress (MWC) in Barcelona, they've opted to host a separate event for the announcement of the Xiaomi Mi 6.
The Xiaomi Mi 6 is rumored to sport a 5.2-inch fullHD (1920 x 1080) display, 4GB / 6GB of RAM and it will probably ship in several storage variants. It is possible this is just a based model, though, Xiaomi might release several variants of this smartphone, one of which will sport a curved display, like the Xiaomi Mi 6 Pro or Mi 6 Plus which were rumored last year. The device will probably ship with Qualcomm's Snapdragon 835 64-bit octa-core processor, at least that's what most rumors have been reporting. Xiaomi might have to wait in order to get their hands on the Snapdragon 835 though, as it seems Samsung picked up the whole first batch of these SoCs, and a ton of other OEMs are interested in utilizing it in their devices.