Alright, this is why I think the next Elder Scrolls game will be and should be set in Hammerfell. Actually, I want the game to be set in both Hammerfell and High Rock so that you could have the complete experience. You have a traditional fantasy setting with the Bretons and a desert warrior culture setting with the Redguards, not to mention the Orcs that have been kicked out of Orsinium.
You would also have more diversity. Not just on race would dominate the game. Nords from Skyrim could be found along the north eastern border. Imperials along the south eastern border and refugees from the Aldmeri Dominion could be hiding in Hammerfell. The Redguards also distrust magic like the Nords, but they take it to a whole new level, persecuting mages and the like. That's why we also need the province of High Rock to balance out the magic and non-magic societies.
I always hear people complain that Hammerfell is just a wasteland. I mean, Bathesda couldn't make an interesting and immersive game set in wasteland right? That was sarcasm. Hammerfell may feature large deserts, but also jagged and even snowy mountains, dense jungles and fertile grasslands and with High Rock, you would also have woodlands, more snowy mountains,
Naval exploration should be added. Having your own ship and crew (the ship would be a player home as well and the crew you could hire) and travel the sea. Better personal stories. Romance along with marriage. Grudges. Becoming a lord and getting a castle, buying towns and villages. That sort of thing. Battles in the war questline should be more epic and huge. With the new generation, I want to see sieges with dozens of soldiers. Imperial soldiers would work as one with the shields, Nord and Redguard soldiers would charge, that sort of thing.
Combat should be enhanced as well as the magic system. Survival elements like eating, sleeping, drinking and proper attire to withstand the elements should add bonuses to your character. They should also add Mass Effect-like dialogue cutscenes to immerse the player in the story. Also, to anyone saying that they should do all of Tamriel, they can't and if they did, it would take to long and it would always disappoint. In takes them years to make a game like Skyrim.
The story
From eighty to one-hundred years after the Dragonborn killed Alduin, the Empire is at war once again.The war in Skyrim continued even after Ulfric and Tullius were both killed. At the end of the war, the Dragonborn was leading an imperial army (it is possible that the Dragonborn switched sides, Bathesda was planing that feature but cut it out). The the Nords and the Dark Elves made an alliance with a cabal of imperial officers and invaded Cyrodiil from the north and the east, taking the Imperial City and deposing the Emperor. The Dragonborn became the new Emperor of Tamriel, now comprised of the semi-independent kingdoms of Skyrim and Morrowind as well as Cyrodiil. High Rock secedes and does not acknowledge the Dragonborn as Emperor and spits into five kingdoms. Some of those kingdoms still stay loyal to the Empire.
Fast forward: The grandson of the Dragonborn, a young Nord sits the Ruby Throne and the kingdoms of High Rock are at war over a territorial dispute. The imperial legion has been sent to aid the kingdoms still loyal to the Empire in conquering the province, Meanwhile in Hammerfell, the Forbearers and the Crowns are in dispute on whether to ally themselves with the divided Bretons or the Empire which has betrayed them in the past. You are released from prison just as the town you are in is attacked by raiders. There has been an increase in raider attacks and necromancer activity in the last few months. Daedra have also been popping up.
Mannimarco, the King of Worms has been resurrected by a reformed Order of the Black Worms. The Hero of Kvatch only destroyed his mortal body. But Mannimarco became the god of necromancers in Daggerfall. He has been gathering strenght ever since TES 4 Anyway, Mannimarco is behind the attacks. The player discovers that the possesses the powers of the Hoon Ding and is like the last Sword-Singer or something and has to discover these black cubes to gain more powers and to learn the way of the voice (it even sounds like a ripoff of the way of the voice), And just as you get about halfway through what you think is the main quest, you hear the news: An Aldmeri Warfleet has just set sail for Hammerfell, hundreds of ships and they carry with them the Thalmor and the Great War.
So yeah, total war. Another thing they should add is more epic godlike enemies and interactions. Like the dragons. The Dragonborn killed alot of dragons, but he made them afraid. There would be less dragons, but when they do show up, it will be epic. Also, the daedric prince quests need to be even better. Picture this: you and an NPC follower that kind of looks like young Sheogorath from TES2 are sent by Sheogorath to destroy this cult or something. Then at the end, it is revealed that the guy was Sheogorath this whole time, transforming before your very eyes. This was Sheogorath's heroic Hero of Kvatch side showing through the madness. Anyway, you becoming his champion, get your prize, but he will call and you later for another quest.
And for the next game, we would have to go to Summerset, Valenwood and Elsweyr to aid the rebels there against the dominion while the dominion is invaded by Paedonya and Thras. Blackmarsh would be a hard sell and coupling it with maybe Morrowind or Akavir since the two are very simillar would be the only way of seeing the full province. I mean, have you ever wondered why we only see part of the province of Blackmarsh in TES:O? It's because non-Argonians can't live there because of the diseases.
Also, if Hammerfell is the next setting, think of all the DLC! Understroyed parts of Yokuda, islands in the Azurian Sea, Thras, maybe that Nymph Monarchy of Pearlbloom Mythic created on The Elder Scrolls Fanon (seriously, Mythic is really talented), Maybe even Alinor. What do you think?