Google has rolled out Android M, or Android 6.0 Marshmallow, to its Nexus line of devices, and some OEM devices are now getting the update. But Samsung's OTA upgrade to the latest Android operating system is still nowhere to be found for most of its devices, including the 2015 flagship Galaxy S6 and Galaxy Note 5.

Now it appears there is a release date coming soon for those devices and more, if a leaked Samsung Android 6.0 update guide proves authentic.

The Samsung "Android 6.0 Update Guide (Phase. 1)," as the header of the leaked document reads, includes a monthly update release date for every Samsung Galaxy flagship from the last two years.

Leaked by "Xtech Leaks" and picked up by BGR, the document provides good news for 2015 and 2014 Samsung Galaxy Note and Galaxy S-model owners, if the document is authentic and the information accurate. That's because it shows most of the Android 6.0 Marshmallow updates coming to most Samsung devices in the next month or two.

Here's the update release date schedule for Samsung's top devices, according to the leak:

Samsung Galaxy S6 - February/March 2016

Samsung Galaxy S6 Edge - February/March 2016

Samsung Galaxy S6 Edge+ - February 2016

Samsung Galaxy Note 5 - February 2016

Samsung Galaxy S5 - March/April 2016

Samsung Galaxy Note 4 - March/April 2016

Samsung Galaxy Note Edge - March/April 2016

In addition, the document shows the status of the updates for every device as "approved." That probably means it's "approved" by Samsung, leaving the possibility open that U.S. carriers may have to finish their testing before the update goes out.

That would add a couple weeks, minimum, to the update release date schedule, but as Samsung described the ETA on these updates on a broad monthly basis, that may be already taken into consideration.

Since Samsung's Galaxy S7 is rumored to be unveiled soon, at the Mobile World Congress 2016 in mid-February, it's nice to see the rest of Samsung's flagship pack will likely be brought up to speed around that time, or shortly after. Since the leak is unconfirmed, though, take all of this with a tiny grain of salt.