The thing about Android is that it constantly needs to be upgraded, and lately, it has been getting a full upgrade (a version that ends with a zero) every year. By now, most of the companies that make Android devices such as Samsung, HTC, LG, and Motorola have been receiving Android version 6.0 (also known as Android M or Marshmallow) on their flagships, and Sony is often the last on this list. This is the latest 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.
Android Pit reports that Sony tweeted that the Xperia Z5 series (the Z5, Z5 Compact, and Z5 Premium), the Z4 tablet, and the Z3+ are all set to receive Marshmallow starting on March 7. On that particular date, Sony announced that the rollout "has begun" on Sony's own Xperia News Twitter Page, but this rollout was reported to be staggered, with different locations receiving the update at different times.
This is not uncommon for Android rollouts, particular when it comes to specific carriers like Verizon, Sprint, AT&T, US Cellular, and T-Mobile, as often one can receive the Android upgrade before the other. If you are a user of any of the Z5 devices, or Z4, or Z3+, then you should check your "Settings" menu as well as "System Update" to see if the upgrade is available for your Sony device now.
In addition to the previously mentioned Z5 Series, Z4, and Z3+, there are other devices that will be receiving the upgrade such as the 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, according to Android Pit. About the only Xperia that is being left out is the Xperia Z1 and the Z1 Compact, as they are older phones, but it is interesting to see that Sony is including the Z2 for the upgrade.
A recent report from Android Authority states that Sony will release an Xperia Z2/Z3 Marshmallow Beta update with bug fixes. The purpose of the beta is so Sony users will try it out, and they have been listening to the feedback. In fact, there have been reports from Z5 users having trouble with the upgrade on their devices. There have been at least two problems, one of them is the double-tap to wake feature, and the other is audio-related problems, according to Neurogadget.
So it looks like the Android upgrade is getting some problems, but at least it is getting out there to Sony. Sony is often the last to receive the upgrade to its flagship phones, and it can hopefully iron these problems out before it offers to the upgrade to its complete line.