Personally, this doesn't grab me a huge deal, I'd be happy for it to take a backseat in the next installment or even just be resolved before the game takes place and explained through lore. I feel, however, it's probably going to feature prominently considering it wasn't exactly at the forefront in Skyrim.

In large part it all depends on the setting, I suppose, were it to take place somewhere like Argonia then I imagine the Empire/Aldmeri Dominion conflict would be almost inconsequential. If it is somewhere where it would be a more pressing matter like Hammerfell though I'd hope it was not the main theme.

I'd personally like to see it over the next 2 - 3 TES games. I can also see how this could lead up to landfall taking place.

I think it's a pretty big deal, personally. I don't really think that it would be best to have a direct hand in the conclusion of it, as I doubt they would be able to adequately portray it in a game, but yeah.

There is also a lot of potential for espionage quests and further factional complications/interactions/conflicts with this overtone.

I feel it is interesting from a lore perspective, the Battle of the Red Ring and all that, entertaining to read about. However I feel like in terms of gameplay it can fall a little flat and would be too similar to the Civil War from Skyrim. We'll see I guess, since it would appear I'm well in the minority here. If there were larger small-scale battles between the Empire and allied forces and the battlemages and mage infantry of the Aldmeri Dominion I suppose it could be quite fascinating to watch and take part in.

And if it is Hammerfell, with its apparent undead problems, perhaps we could also see a rogue Aldmeri Dominion general raise, enthrall and command an army of undead and unleash it upon the region.

Could we see a return of Mannimarco? Or a figure actually worthy of usurping the title of King of Worms?

I think we could see Mannimarco if a game were in Hammerfell. I doubt he'd have much of a presence in the ongoing conflict, other than perhaps using Sload to help him collect casualties from the battles. Still, I don't even think there would be a war in Hammerfell. I think that would probably be reserved for the final game in the arc.

In Daggerfall, as far as I'm aware, Mannimarco's fortress was in Hammerfell. We'll probably definitely at least see the ruins of his old keep. I don't see why they wouldn't bring him back, though (in the event of the game being there), considering that the Sload are supposed to be prominent enemies in Hammerfell and would probably worship him heavily. Honestly, I'd support them making the entire order of the black worm joinable.

Also, I think largely it depends on how the ongoing war is depicted. For now, I approve of small, espionage-like conflicts and perhaps pro-Thalmor terrorism taking place at random locations in the games until the final part of the arc. I think a full-on series of battles taking place at worst could be done similarly to Skyrim, but at best, could be done much better. We also have to think about how much technology will develop by 2 - 3 TES games from now. That's probably about a minimum of maybe 15 years away. I think they'll be a lot more capable of pulling something high-scale off and for it to be rewarding in around this time.

I think the best thing that should happen regarding the overarching plotline for the time being, are numerous espionage and conspiracy-related things. Collectively, they could add a climate of paranoia (especially if betrayal, corrupt politics, and spies were something portrayed well) and political creepiness. I also think it would be interesting and really creepy to have an occasional "Thalmor interrogation/experimentation camp" pop up, or something of the sort, where people are tortured and experimented on using magic and magical technology by Thalmor agents.

I hope so, even coming across his old fortress and finding relics and potentially journals and writings from him would be awesome. I agree if he and a faction of his were to feature in the game it would be nice to actually be able to join them instead of just defeating them.

It would be cool perhaps if the game started with like a goblin rebellion, tribes of goblins (including giant goblins, prevalent in Hammerfell I believe) were moving across the desert and attacking the cities of the coast for unknown reasons. Upon infiltrating the goblin tribes you come to learn that they are actually fleeing from vast armies of undead that have begun rising from the sands.

Rumors attribute this to a powerful cult of necromancers in some isolated region of Hammerfell which turn out to be affiliated with Mannimarco (or a usurper claiming his title at least, perhaps a rogue Aldmeri general as I suggested, who was still extremely powerful) and the Order of the Black Worm. Then you know the rest, with ideally the option to join them at some point and help them overrun and decimate Hammerfell with hordes of the undead.

Perhaps you are pressured over the course of the game by agents of the Empire and Aldmeri Dominion to command his army upon defeating him (assuming you choose to) instead of destroying it and use it to aid either side in their fight against the other, sort of like a New Vegas situation.