I would love to see a TES set in Black marsh, or maybe the wood elf home land (think its valewood) but what I've always wondered is if TES could go back in time to when daedra walked the earth the dwemer where discovering new technoligies while at the same time the rise of the legion and tiber septim. It would mean real conflicts between not only factions but races like if you were dwemer you'd be hated by dunmer and being a daedra would be so badass. With this there could be not just the mortal world but every realm you could visit this would truly bring a multiplayer aspect, maybe a bit like wow because I'd love to see a multiplayer TES and I think it could happen.
I don't think we'd be able to give Black Marsh justice right now. I think we should cover the more "simple" provinces first. Black Marsh should be the last on the list. Followed by Valenwood. the next in the line of difficulty would be Summerset. But I think we could give it justice now.
I think I read somewhere that we're not going back in time through the games. We're following a timeline. Maybe this meant we're not going back eras, or the other way around, I don't know. I'd actually like to go back in time in some RTS spinoffs to see some wars. Could be nice. (Note - spinoff ONLY)
There's been so many awesome wars throughout the games we've missed. out of game lore is so awesome...
And you're going to be eaten if you mention multiplayer. Especially MMO form.