As Krisztián already wrote, the production of the Mi 9 phone has been stopped, and only the existing stock is available. The primary reason for this is the start of production of the next phone.
The news of Xiaomi Mi 10 should not come as a surprise to anyone, as the company's top phones are usually released in the first quarter of the year and the news and rumours start coming in early in the year. Interestingly enough, a very important hardware unit, the processor type, was already revealed at the beginning of December at today's Qualcomm conference, where it was introduced by Xiaomi president Lin Bin.
The Xiaomi Mi 10 will be one of the first phones to use the Qualcomm Snapdragon 865 processor, but in China for sure. At the conference, Lin Bin mentioned, or rather confirmed, that Xiaomi will launch at least 10 5G-capable phones in 2020.
Almost nothing is known about the processor yet, only a few things were revealed at the conference, such as the new X55 modem with dual 5G support, the new 3D Sonic Max fingerprint reader that supports 17x larger readers than before.