Images by Apple, Huawei, Samsung (Source)
Samsung is the producer of the 200MP sensor, but another company will use this first on one of their phones.
The Samsung ISOCELL photo sensor of 200MP will have of 0.64 microns pixel size and will be used on a Xiaomi phone, but we don't know yet which.
Initially it was thought that the first smartphone with this camera would have been the ZTE Axon 30, but seems it wasn't true. The Xiaomi phone will do 50 MP photos, combining pixels, having a 1.28 microns size. That means photos with better details and more light.
A bigger sensor means a better and bigger digital zoom. At this moment, the 108MP sensor can do 2.3x zoom. The 200MP camera will, in theory, do 4x or 5x zoom without quality loss, and even 16k video recording.
It remains to be seen which Xiaomi phone will have this huge camera.