Considering that Samsung is one of the biggest cheerleaders for Android, one would think that the latest version of Android 6.0 (also known as Android M or Lollipop) would have arrived on its devices by now. The latest version of Android will arrive on Google's own Nexus series and then will slowly roll out onto many Android devices like those from HTC, LG, Sony, Motorola, and, of course, Samsung. This is what is currently known and rumored about the Android M Version 6.0 Marshmallow Release Date for Samsung Galaxy S5, Note 5, S6 Edge+, and Note 4 on carriers such as AT&T, Verizon, T-Mobile, Sprint, and US Cellular.
A recent report from Mobipicker states that users of the Galaxy S5, S6, S6 Edge, S6 Edge +, Note Edge, Note 4, and Note 5 are in for some good news. There has been a leaked source known as "XTECH LEAKS" who has shared an image of the roadmap of Samsung's Marshmallow rollout schedule. This leaked roadmap matches a lot of other sources, with predictions of the Android rollouts arriving on Samsung devices later than expected in 2015.
According to this supposed leaked schedule (which should not be considered a 100 percent reliable source) states that the Galaxy S6 Edge + and Galaxy Note 5 will be the first devices to receive the Android M upgrade, sometime in February. Even though I said earlier that this source hasn't been completely confirmed, it at least makes sense as the S6 Edge + and Note 5 are the most recently released devices.
Once the S6 Edge + and Note 5 are taken care of, then it would be on to the Galaxy S6 and S6 Edge, the company's flagship phones for last year, receiving the upgrade, probably sometime in between February and March. This would mean that flagship devices from two years ago like the Galaxy S5, Note 4, and Note Edge, will be getting the Android 6.0 upgrade around March to April. Other devices slated to receive later the update include the Samsung Galaxy A8, A7, A5, A3, E7, and E5, as well as Q2 updates for Samsung tablets like the Galaxy Alpha, Galaxy Tab A, Galaxy Tab S2 9.7, and Tab S2 8.0.
As far as what devices won't be receiving upgrades, it looks like any Samsung flagship older than the S4 won't be receiving its update, and that goes for the Note 3 as well. When Android Marshmallow does completely roll out to Samsung devices, it might also depend on the carrier. Sometimes, in the United States, certain carriers like US Cellular, Verizon, Sprint, T-Mobile, and AT&T and achieve the latest upgrade of Android before others.