Back in 1994, when Bethesda released The Elderly Scrolls, Arena, its gameplay featured the entire landmass of Tamriel, making it the largest game of that time. This was also how the audiences were introduced to all the 9 provinces lying in Tamriel. However, the vastness of the landmass did put some restriction on the details, resulting in little landscape variation from one end of Tamriel to the other.
The latter sequels were however limited to one or two provinces, with increased focus on the details. When Daggerfall came out in 1966, its explorable area was limited to only High Rock and Hammerfell. This was actually a wise step as it allowed the developers to pay close attention to a smaller section while greatly boosting the graphics and gameplay. After that, Bethesda seems to have been pretty impressed with the idea which is why it continuously gave out games that were set in just one province. Morrowind was based in the island of VVanderfell, Oblivion was set in Cyrodil and Skyrim in Skyrim itself. This leaves four provinces that have yet been untouched – Black Marsh, Summerset Isles, Valenwood and Elsweyr. There is a high possibility that The Elderly Scrolls 6 will be taking place in one of these provinces, or it is also possible that it will feature an older province on an entirely new game engine.
Speculations have been high that The Elder Scrolls 6 location is going to be Black Marsh and that the sequel is going to be called Argonia. But given that there have not been any official announcements so far, it would be better for us to refer to the game as TES6 or The Elderly Scrolls 6. When considering if TES6 is actually going to be set in Black Marsh, some aspects do come into question. For example, Black Marsh consists mostly of swamps and jungles; it is doubtful whether such a terrain is going to provide interesting gameplay. Elsweyr on the other hand has a more varied landscape, comprising of deserts and forests, which is why it remains a viable candidate for TES 6 location.
Considering how a game set in each of the four provinces would look like, the following can be deduced.
First of all, Valenwood is like some sort of dense rainforest within the Tamriel and much of it remains unexplored. It is home to the Bosmers or Wood Elves and their cities are full of greenery and massive trees called Falinesti. This could mean a lot of interesting visuals. Also, in the present political scene, Valenwood remains under the Dominion Rule which is hated by many elves including Malborn from Skyrim. This allows for some engaging gameplay, where a player can either play to support or detest the quest for independence.
The current political scenario in Elsweyr is favourable as an interesting background story for TES6. Home to the Khajiits, this province was believed to be ruled traditionally by the Mane, a spiritual leader of the feline race, who was born during the alignment of two moons. However, after killing the last Mane, the Aldimeri have taken control of the land. The game may feature a rebellion to overthrow the Aldimeri Dominion. The province also has a varied landscape, deserts to the north and dense tropical forests to the south. All of these factors combined make Elsweyr a favorable The Elder Scrolls 6 location.
Summerset Isles consists of three major islands and the province is supposed to be full of magic. The cities in Summerset Isles have glass fortresses and crystal castles. Although it is currently under the rule of the aristocratic leader Thalmor, the Stormcloak general Galmer Stone-Fist is likely to carry an attack on the province. This makes the Summerset Isles no less interesting as Elder Scrolls 6 location.
The most important reason as to why Black Marsh remains the most viable candidate for The Elder Scrolls 6 location is because of its vastness. The province is full of wetlands and marshes, making it habitable mainly for the reptilian natives. It is home to the Argonian culture and given that the Argonians are pretty much oppressed in all other parts of Tamriel, it could make for an intriguing political plot.