The roadmap of Samsung devices software updates just leaked and according that the Galaxy Note 5 is the first will get the software updates and for this Samsung already upgrade their TouchWiz users interface. Galaxy S6 Edge Plus is standing in the 2nd step and will be updated in December according to the previous schedule, but now the Galaxy S6 Edge Plus will be updated in January 2016.
The Galaxy S6 and Galaxy S6 Edge have the same updates plan and will get the Marshmallow treat in January. The Galaxy Note 4 and Note 4 Edge will be updated in Feb and the Galaxy S5 will get the software update in April. The Galaxy A8 users will get the Marshmallow updates in March.
As per the latest list, there are almost all A, E and J series are included for getting the updates of Marshmallow soon, but, unfortunately, the Galaxy Note 3 and Galaxy S4 is not mentioned in the list anywhere. Well maybe later these devices will also get the Marshmallow treat.