Well, we have been having the last version of Android Version 6.0 (also known as Android M or Marshmallow) come out on many Android devices from companies like LG, Samsung, HTC, and Motorola. The issue is that it has been slow to come out to Sony, who is still a major player of Android in most countries, even in the United States. This is what is known about Android M Version 6.0 Marshmallow and Android N Release Date for Sony Xperia Z5, Z4, Z3, and Z2 on Sprint, AT&T, T-Mobile, US Cellular, and Verizon.
So, I'm sure that the current flagship of Sony Xperia Z5 phones that include the Z5, the Z5 Compact, and the Z5 Premium have their upgrade done. Well, I am pretty certain that it has it, as there was a lot of chatter on Twitter to make certain that it was going to be out on March 7. As for the Xperia Z3 and Xperia Z2 series, there is still talk about them having Marshmallow in beta form.
According to Know Your Mobile, Sony has issued a note on its Android Marshmallow plans for Xperia Z2, Z3, and Z3 Compact. The Xperia blog says: "Sony Mobile has commenced the Android 6.0.1 Marshmallow rollout on the Xperia Z2 and the Z3 series. The update is currently live for the Xperia Z2 (D6503 only), Xperia Z3 (D6603 ony) and Xperia Z3 Compact (D5803 only). The new firmware has build number 23.5.A.0.570, which incidentally is the same as the recent beta release."
There is a report on the International Business Times, the Japanese company had seeded the Marshmallow beta with a new feature called "soft charging" to the Sony Xperia Z2, Xperia Z3, and Xperia Z3 Compact which gives a hint that a firmware update will be coming to these devices soon. The soft charging will extend battery life and the update comes with a build number 23.5.A.1.238 and the Xperia Home launcher that can fix bugs.
Sony seems to be very slow about getting Android Marshmallow onto their latest flagship phones, and for April 11, Sony will continue the Xperia Marshmallow preview into the summer. Yes, that isn't really good, considering that most of the recent Android devices from other companies already have this upgrade. It will more than likely take even longer to get the just-announced Android N onto Sony products.
The best and only advice one can give a Sony user of a newer device in the United States is to see if you can't get the OTA (Over The Air) download now. Just go into the "Settings" and "System Update" to see if the upgrade is available. The upgrade may not be available depending on your carrier 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 on your Sony device, as well as what carrier that you subscribe to.