They will be followed by the Galaxy S6 and Galaxy S6 Edge in January. The third wave of upgrades is  scheduled for February and it will include Galaxy Note 4 and Galaxy Note Edge phones.

All these phones have been already approved for an update. The Galaxy S5 and Galaxy Alpha phones are still awaiting  approval. The first phase of upgrade ends with these devices.

The second phase includes Galaxy A8, Galaxy A7, Galaxy A5, Galaxy A3, Galaxy E7 and Galaxy E5. All these devices are still waiting for approval.  

The Android upgrade cycle and its delays have been a cancer of the whole ecosystem and Samsung is not immune. The company allocated a  significant number of engineers to offer these upgrades. Soon after the top 2015 get Android 6.0 it will be the time for Samsung Galaxy S7 launch.