Most smartphone manufacturers like Samsung, Sony, LG, HTC, Motorola, Xiaomi, OnePlus and others have already declared the list of devices that are eligible to receive Android 6.0 upgrade. From the start of 2016, the Android 6.0 update will be made available for devices from these brands.
According to GSM Arena, here is an official list of devices across different smartphone brands that are going to receive Android M update at the start of this year.
The Samsung Galaxy S6, S6 Edge, S6 Edge+, Note 5 and Galaxy Tab S2 devices from 2015 are going to receive Android 6.0 upgrade first. The 2014 Samsung devices that will also be given priority to receive Marshmallow firmware upgrade includes Galaxy Note 4, S5, Alpha, A8 and A7.
Sony Xperia Z5, Z5 Premium, Z5 Compact, Z3+, Z4, C5 Ultra, C4, M5 and M4 Aqua from 2015 are going to be updated to Android 6.0 soon. The next set of devices that will receive Android 6.0 are Xperia Z3, Z3V, Z3 Compact, Z3 Tablet Compact, Z2 and Z2 Tablet. The Sony Xperia Z Ultra GPE from 2013 is also poised to receive Android M update soon.
LG will first release Android 6.0 upgrade for its major smartphones from last year such as LG V10, G4, G Flex 2, G4 Stylo. The update will be also widely available for LG G3 users.
The first set of HTC devices that will be updated to Android 6.0 from the beginning of 2016 are HTC One M9+, One E9+, One M9, One E9, One ME, Butterfly 2, and Desire 826. The HTC One M8, One E8, One M8 Eye, Desire 820 and Desire 816 from 2014 are also going to get upgraded to Android M soon.
Moto X Pure Edition (2015), Moto X Style, Moto X Play and Moto G (2015) that released last year will first receive Android 6.0 upgrade. The firmware upgrade will also arrive for 2014 Motorola devices like Moto X Pure Edition (2014), Droid Turbo, Moto Maxx and Moto Turbo.