We know for a fact that Android version 6.0 (also known as Android M or just Marshmallow) is starting to rollout to a lot of Android devices. We also know that Sony devices like the Z5 series, Z4, Z3 series, Z2 series, as well as the M5, C5 Ultra, M4 Aqua, and C4 are expected to receive it. The issue is that the rollout has been slow for Sony, and this is the latest news about the Android M Version 6.0 Marshmallow Release Date for Sony Xperia Z5, Z4, Z3 and Z2 on Sprint, US Cellular, T-Mobile, AT&T, and Verizon.
So yes, there are a lot of Sony Android devices that are going to receive the Marshmallow upgrade. The most obvious to receive the upgrade first would be the Z5 series, which includes the Z5, the Z5 Compact, and the Z5 Premium. A report from Android Authority on the Marshmallow upgrade has revealed that the upgrade has come to the Z5 on an International level as of March 7. The same news has come for the Xperia Z4 Tablet as well as the Z3 Plus.
In fact, a recent report on Yibada stated that Verizon, AT&T, Sprint, and T-Mobile are expected to release Android 6.0.1 for these aforementioned models of Sony devices "soon", possibly by April. This report is about a week old, and last week we reported that a lot of Z5 users were getting a lot of bugs associated with the update. There hasn't been as much news this week about the bugs as there was last week.
Various support forums saying that their phones have "crashed" with a pop-up window saying "Google Play Store has stopped". Sony responded by suggesting their consumers go with a factory reset, and some users said that resolved the issue while others said that their problems continued.
As far as variants of the Xperia Z2 (D6503), Xperia Z3 (D6603), and the Z3 Compact (D5803) are concerned, users of these devices also have reason to celebrate as NDTV revealed that Sony began rolling out Android 6.0.1 to these particular devices over the last weekend. This report says that the update for now is limited to the variants listed above, and to the United States, Latin America, Middle East, North Africa, Russia, and Ukraine, with availability for more variants in more regions happening soon. There are reports that the Xperia Z3+ and the Xperia Z3 is receiving a beta version of Android Marshmallow.
So it is possible that if you have a Sony product, you might be quite eligible to be the upgrade. If you want to do that, you could go to the "Settings" menu and check the "System Update" to see if it is available. However, you could unintentionally download that bug that has been getting people upset, so it is a risk on your part.