New lands to the east or the west so hammerfell , highrock areas or even better a piece of morrowind ...
I agree about the spears(we already know they worked on them during the game jam), but I doubt we'll see this, at least in Hearthfire. I'm expecting Hearthfire to be one of the smaller DLCs, probably $10, and will simply introduce spears, maybe spellmaking, and a short quest with the College. Though I'm not sure how that would fit into the title....maybe it's a "Winterhold Rebuilt"-type deal, and hearthfire isn't referring to the month, but the actual hearths which warm the new houses of Winterhold? I got nothin', my only real expectation is that it won't be very big.
I do think there's a possibility of visiting a part of either High Rock or Morrowind in the "big" DLC, though, which will probably be the third or fourth(and last) DLC. High Rock
would have the edge since we've already explored it in Daggerfall, but I can't imagine them doing an entire province for a DLC and there's no real natural point in the geography where you can logically say "OK, we'll stop here." It would be an all or nothing thing. That's why I think it's more likely that if we get to explore another province in future DLC, I think we'd be looking at exploring a chunk of morrowind, namely the area surrounding Black Light, and which borders on Skyrim. There's a chokepoint there as you go south to mainland Morrowind where you could add the invisible walls, a huge in-land sea to keep you from reaching Vvardenfell or other portions of Morrowind, and the region isn't unreasonably large. There's also the fact that we're teased about what's going on in Morrowind in Windhelm a bit. (I also kind of like the idea that no single TES game will fully explore Morrowind, but that's just a personal sentiment)
That said, I wouldn't be surprised if the "big" DLC simply takes place in another Daedric Realm. I'm also not entirely sold that there WILL be a big, Shivering Isles style DLC; so I'm going to remain skeptical of the whole idea.