The upgrade to Android 6.0 (also known as Android M or Marshmallow) has been available for a few months now, and it would seem that most of the Android devices from Samsung, HTC, LG, and Motorola have their upgrade on their latest flagships, but there has been some mixed information when it comes to Sony's devices. This is the current news about Android M Version 6.0 Marshmallow Release Date for Sony Xperia Z5, Z4, Z3, and Z2 on Sprint, T-Mobile, AT&T, US Cellular, and Verizon.
There is good news for anyone who had the Xperia Z3, Xperia Z3 Compact, Xperia Z2, and Xperia Z2 Tablet. The update is available Over The Air (OTA) or via Sony's PC companion app, provided that you are in India, according to the Indian Express. It is possible that Sony is releasing it in India in preparation for a worldwide release date, and many Android smartphones have a pattern of releasing similar to this.
If you are a Xperia Z3 or Xperia Z2 user, you might have the Android upgrade available to you already. Android Pit says that it is available for the Xperia Z3 and Z2 as well as the Z3 Dual as well, but it didn't specify what country or carrier this availability exists.
Normally, the rollout for Android often takes place in the chronological order of the device, with the newest receiving it first and the oldest getting it last. It looks like this might be taking place, as the rollout for the Xperia Z5 series, which includes the flagships of the Z5, Z5 Premium, and the Z5 Compact have happened already. The date was set for March 7, but whether or not that has happened or not is vague, as the previously mentioned report from Android Pit states that the Z5 update is "Confirmed" and not "Available." The same "Confirmed" stamp is given for the Xperia Z4 Tablet, the Xperia M4 Aqua, the Xperia C4, and Xperia MS, with no release dates confirmed.
The fact that the Z3 and Z2 have received an Android upgrade first goes against the pattern of the rollout. The bottom line is if you have a Sony Android device that is relatively new, then you should go into the "Settings" and "System Update" to see if the upgrade is available. As stated before, the upgrade may not be available depending on your carriers like T-Mobile, Sprint, US Cellular, AT&T, and Verizon.
If you have a Sony device, particularly a new one, and have received the upgrade, go ahead and leave a comment with your device's name and carrier, so that we can have some hands-on information about the accuracy of the upgrade availability for Sony devices.