According to a Korean publication, Samsung is currently busy putting the Snapdragon 820through some very intensive testing. The results of all those tests will have a bearing in whether Samsung decides to use the Snapdragon 820 in the Galaxy S7 or not.
At the moment things seem to be going well, which means we may once again see a Samsung flagship with two SoC choices, each offered in certain markets only. This was the case for a few years, until this year when the Galaxy S6 only went with Samsung's own Exynos chipset. The reason for that probably has something to do both with the performance of the Exynos 7420, but also with the much-publicized overheating problems that the Snapdragon 810 encounters.
Its successor, the Snapdragon 820, is set to be quite different in that regard, though, so it may once again be seen in a high-end Samsung device.