After 4-to-1 Quad Bayer technology in cameras, it's only natural that 9-to-1 pixel binning will also arrive in smartphones [COMPACTIDEA]

https://www.gsmarena.com/explaining_huawei_p20_pros_triple_camera-news-30497.php

From my perspective, Quad Bayer technology's benefits come into play only when taking HDR images - zero-delay HDR images, that is ["simultaneous", rather than "sequential"]. For regular, non-HDR images, the binning doesn't do anything extra compared to what a same-sized non-binned sensor with fewer [but larger] pixels would accomplish. Of course, one other thing that such binned sensors do accomplish is easier marketing - Chinese companies such as Xiaomi, Realme, etc., proudly tout "64 MP" images without telling the public that the images captured and actually stored in their cameras are only 16 MP.

Anyway, it's my feeling that after this hoopla around 4-to-1 becomes boring, camera/phone companies will bring in 9-to-1 pixel binning, because it'll allow them to market small-sized sensors with huge megapixel numbers [imagine a 270 MP 9-to-1 sensor that outputs a 30 MP image]. Of course, 9-to-1 binning will be great for HDR images. It might capture 3 shots at once and then merge those into a single HDR image with lovely colors. Who knows, we might get to 16-to-1 binning, etc.

Update [17-Dec-19]: And it's here :-)

Samsung Galaxy S11 to feature 9-to-1 Bayer sensor on its 108MP camera
https://www.gsmarena.com/samsung_galaxy_s11_to_feature_9to1_bayer_sensor_on_its_108mp_camera-news-40581.php

Huawei P40 Pro to have a Sony-made Quad Quad Bayer sensor, dual prism zoom camera
https://www.gsmarena.com/huawei_p40_pro_rumored_to_have_a_sonymade_quad_quad_bayer_sensor_dual_prism_zoom_camera-news-41069.php

"New info suggests that this sensor will be a custom design by Sony and will feature “16-in-1” technology.

It’s also called “Quad Quad Bayer” as it does two 4-in-1 conversions to reach the 16-in-1 stage. This will only be used for videos and photos shot under very dark conditions."

Update [1-May-20]: Samsung is pretty sure that more and more megapixels are its sure path to higher market-share in the image sensors business.

Samsung to deliver a 250MP sensor
https://www.gsmarena.com/samsung_also_working_on_a_250mp_sensor-news-42938.php

Samsung aims to develop a 600MP camera sensor
https://www.gsmarena.com/samsung_aims_to_create_a_600_mp_camera_sensor-news-42773.php