Samsung did Android customization the Wrong Way™; their modifications are deep, and any update is always going to require a lot of resources to adapt and test. Plus, they have a gazillion models.
By opposition, Motorola did it the Right Way™; the modifications to the base Android system are minimal, most of what they did is they have added apps, which are on Google Play so they can be updated outside of the Android release cycle.
If quick updates are important to someone, Samsung does not get a good score on that front. I had Marshmallow on my Nexus 5 back in November, when S6 owners were struggling to get 5.1.
Great news!! Samsung has finally begun releasing Marshmallow for the Galaxy S5 (see here). Although it will still likely be a couple of months before we actually see the update, the ball has started to roll
Thats only for the South Korean version the W8 which is for Canada is still in development....
We are well aware that the release was for the South Korean version. The fact that there is any version released is progress!
According to Samsung its still in development so we are not sure of the release date.
You can see here.
Once Samsung releases the update we will still have to wait for the carriers to release it.