Android 6.0, also known as Marshmallow or Android M, has been released for about two months. As the tradition goes, Google's own Nexus devices are the first to pick it up, and then it slowly comes to other Android devices. When it comes to Sony and their Xperia series, it has been known to roll out a lot slower. This is what we know about the Android M Version 6.0 Marshmallow Update Release Date for Sony Xperia Z5, Xperia Z4, and Z3 on carriers like Verizon, AT&T, Sprint, US Cellular, and T-Mobile.
According to Trusted Reviews, Sony promised a pretty swift update for Android 5.0 (also known as Android L or Lollipop), but it took the company months before all its customers were finally given the update. Not only that, the launch of 5.0 on Sony's products wasn't exactly a smooth transition, so perhaps version 6.0 will be better.
As far as what devices will be receiving the update, there isn't a set release date for all of their devices. This is the ones that are sure to get it, slowly but surely: Xperia Z5, Xperia Z5 Compact, Xperia Z5 Premium, Xperia Z4 Tablet, Xperia Z3+, Xperia Z3, Xperia Z3 Compact, Xperia Z3 Tablet Compact, Xperia Z2, Xperia Z2 Tablet, Xperia M5, Xperia C5 Ultra, Xperia M4 Aqua and Xperia C4.
Know Your Mobile says that Sony has confirmed that it will be updating several of its Android handsets and devices in the coming months. Two weeks ago, it reported that the entire Xperia Z5 line-up will be receiving the update in January. That means the Z5, the Z5 Compact, and the Z5 Premium should be receiving it first, and then older models like the Z4 and the Z3 series should be receiving it in February at the earliest. This is leaked information, so it should be taken with a grain of salt as far as when the actual release dates will be.
Speaking of information that might not be quite reliable, Xperia Sony has stated that Sony has released binary images of Android Marshmallow beta for the Xperia Z1 series, even though the Z1 was not on the list above.
According to Android Community, Android Marshmallow has been Wi-Fi certified for the Xperia Z4 and the Xperia Z5, or, at least, the Japanese versions have. That is a good sign that the company is at least somewhat on track with updating its Android software, but not enough information to accurately predict when the release date for Marshmallow in the United States will be.
So hopefully, the Z5 will be receiving its update sometime after New Year's Day, but considering that Sony has been slow in the past, it could be delayed in the present. The delay could also come from the carrier, such as Verizon, AT&T, Sprint, US Cellular, T-Mobile, or Verizon, but at this point, it is too early to say.