Usually Google Nexus devices are the first devices to receive latest Android OS updates. Google has released a Preview Version of Android M for selected nexus devices. The Preview version Android M Developer Preview is Available for Download.
Nexus 5 – Download Android M
Nexus 6 – Download Android M
Nexus 9 – Download Android M
Nexus Player – Download Android M
Samsung has not made any official statement about Android M update schedule. However, Your mobile Website has a list of Samsung devices which is going to get Android M update by the end of this Year. I am not sure the list is official or not. But I know you would love to hear this information anyway.
Samsung Galaxy S6
Samsung Galaxy S6 Edge
Samsung Galaxy S6 Duos
Samsung Galaxy Note 4
Samsung Galaxy Note 4 Duos
Samsung Galaxy Note Edge
Samsung Galaxy Alpha
Samsung Galaxy Tab A
At the very least I assume both Samsung Galaxy S6 and S6 Edge will be the first Samsung devices to get Android M update this Year.
Sony is remaining silent on Its Android M Update Schedule, but Sony’s Xperia Series Devices Z3, Z3+ and Z4 Tablet will certainly get Android M updates before the end of this year.
Typically Motorola Phones get Android updates quickly. So I guess the Moto X will be the first Motorola Phone to get Android M update. But other Motorola models Like Moto G (2nd Generation) and Moto E (2nd Generation) also have chances to get Android M update.
Still Motorola has not received Android M source code from google. Once Motorola get the Source Code, they will prepare Android M for their Smartphones.
HTC’s Global Online Communications Manager Jeff Gordon Announced that HTC One devices M9 and M9+ will be the first HTC Devices to get Android M update. It’s not clear but those devices will get Android M update in the next 3 months.
LG also has no Official Word on Android M update, however The LG G3 and G4 will definitely receive Android M update. on the other side LG’s Greek Facebook Page announced that they have no plans for Android 5.1 update for G3 devices. possibly they are going skip straight to Android M.