When Android rolls out on everything but Google Nexus, it tends to rollout slowly. Even one of the biggest carriers of Android, Samsung, never gets right away, but this is what is currently known about the Android M Version 6.0 Marshmallow Release Date for Samsung Galaxy Note 5, S6 Edge Plus, S6, S6 Edge, Note Edge, Note 4, and S5 for Verizon, US Cellular, AT&T, T-Mobile, and Sprint.
According to Tech Times, the beta Android 6.0 Marshmallow update has arrived to Samsung's 2015 flagship smartphones, the Galaxy S6 Edge and Galaxy S6. This update was limited to a handful of users in the UK and did not make its way to users in the United States.
Most information on the release date of Android Marshmallow is actually before the holidays, so it seems a bit old. For example, a report on Pocket-Lint states that the first phase of Android 6.0 were going to be landing on the Galaxy Note 5 and the Galaxy S6 Edge+, which are the latest of the Samsung Android devices. It doesn't look like that deadline has been made for any carrier.
This source also said that the Galaxy S6 and the Galaxy S6 Edge would probably receive their Android update by January 2016. Considering that the beta arrived earlier than that, this is confirmation that perhaps Marshmallow will be out on the S6 and S6 Edge before the end of January.
Next on the update list for the rollout would be "older" versions of the Note, such as the Note Edge and the Note 4. Android 6.0 is apparently due to come out on these by the end of February 2016.
After that, the next Samsung devices in line for the update include the Galaxy Alpha, Galaxy S5, Galaxy A8, Galaxy A7, Galaxy A5, Galaxy A3, Galaxy E7, and the Galaxy E5.
Greenbot reports that updates with Samsung are very difficult to nail down because the company sells so many versions of essentially the same device. This means that one Samsung device could receive Android 6.0 before the same device on a different carrier. This also means that when Android Marshmallow officially rolls out, when a subscriber gets it will vary greatly depending on their individual carrier. T-Mobile has now listed its first wave of Android devices set to receive Marshmallow, which includes the Galaxy Note 4.
The past few years of new Android rollouts have shown that it often takes a few months for Samsung to push out major OS updates, and so Samsung users should be prepared to be patient. Samsung is usually good on getting the latest version to most of its devices, provided they are not too old. For example, many believe that the S4 could receive Marshmallow, but there isn't really a list of what devices or when they will receive the update from the big Korean company as yet.
One of the best sources so far for the Android update is a leaked roadmap from Vietnam, which can be found on Android Pit. It puts everything to be receiving an Android update around Q1 or Q2 of 2016, which sounds pretty accurate.