Sony Xperia Z4 and Z5 is spotted in japan Wi-Fi certification database with Android 6.0 Marshmallow. This shows that the official update for these devices are on track and may hit the devices all over the globe in January.
The Wi-Fi Alliance is a Wi-Fi certification database that plays a major role in certifying devices and developing the wireless certification standard. Any new device has to go through the Wi-Fi Alliance in order to receive certification that proves it’s Wi-Fi compatible, and existing devices have to go through the same process again before getting a new firmware version. This is the indications that when certain devices could be getting new Android updates. With that in mind, the fact that Sony Xperia Z5 and Xperia Z4 models passed through the Wi-Fi Alliance now and received Android 6.0 certification for some Japanese models indicates that the Marshmallow update could soon roll out.
Android 6.0 Marshmallow was Wi-Fi Certified for the Sony Xperia Z5 on NTT docomo (SO-01H), SoftBank (501SO) and au (SOV32) as well as the NTT docomo Xperia Z5 Premium (SO-03H). The latest Android version was also certified for the Xperia Z4 on NTT docomo (SO-03G), SoftBank (402SO) and au (SOV31).
Moreover here is Sony’s list of devices that were officially confirmed to get Marshmallow: