Lin did not share much, other than the fact that this phone will be launched in January, and apparently "has used it for a few weeks, not bad!" If everything goes well, Xiaomi can very well end up having the world's first smartphone with a 48 megapixel camera, and it's likely that it will either contain the Sony IMX586 or Samsung's ISOCELL Bright GM1
While both sensors have a small 0.8 micron pixel pitch, they can utilize pixel binning algorithms to merge four pixels in one to simulate better light sensitivity of 1.6 micron pixels in dark environments (meanwhile, many use flagship phones 1.55 micron sensors). When there is plenty of light, 48-megapixel resolution gives a smooth digital zoom with minimal loss in detail – you can do a 4x zoom and still have a native 12 megapixel crop. Similarly for electronic stabilization for video recording.
Still, at the end of the day, it's about how well your smartphone labels your cameras, and it's honest, this has not been Xiaomo's strong point. Hopefully, the company can surprise us all with this mysterious phone coming in January.