Today, Google is planning on announcing a lot at their I/O Conference taking place this week, and there should be something along the line of the latest version of Android with Android N. It is interesting that a lot of the major companies that manufacture Android devices have Android M (also known as version 6.0 or Marshmallow) but Sony is a little stilted as far as its release dates. This is the latest news on Android M Version 6.0 Marshmallow Release Date for Sony Xperia Z5, Z4, Z3, and Z2 on Sprint, AT&T, US Cellular, T-Mobile, and Verizon.
The issue with Sony is that they are running a beta program to test out Android M, and they might be doing it until it finally rolls out on all of its devices. In the meantime, there have been reports of rollouts for the latest flagship series that includes the Z5, Z5 Compact, and the Z5 Premium. The issue is that these reports on Android Authority come from International and Canadian variants of these Android devices.
Not only that but these reports are over a month old. It is odd that reports like these, which constantly update themselves due to the changing nature of Android rollouts, haven't received a more accurate reflection of what is going on. This is assuming that Android M hasn't been released to Sony's flagship series of phones, which really should have by now. All of the other companies of Samsung, LG, HTC, and Motorola pretty much have it.
In fact, there seems to be more news that the Xperia Z3 and the Z2 series are getting the upgrade faster than the Z5 series. By the way, there was a Z4 in there as well, and the update kicked off for that, so I have been told, at least internationally. Much of the news about the Z3 and the Z2 says that its update is available for an OTA (Over The Air) download, which is odd for older devices to receive it before the newest ones.
If you have one of Sony's newer phones, and you live in the United States, it is highly suggested that you should go into the "Settings" and "System Update" to see if the upgrade is available. The upgrade may not be available depending on your carriers like T-Mobile, Sprint, US Cellular, AT&T, and Verizon. Feel free to leave a comment here saying whether or not you received your Marshmallow, as well as what carriers that you subscribe to.