No one talks about Arena anymore (at least not enough to matter in regards to this topic), but I will say something about the fans:
Daggerfall - Politics and lore made a slew of fans, but the sheer size was so novel that many flocked to it
Morrowind - Graphics and depth of story coupled with a scaled down size that seemed manageable and real, but mellowed on the politics
Oblivion - A whole new generation and the graphics were cutting edge for such a big game. It drew in action gamers that had never picked up an rpg, and instead of mellowing politics, nearly removed them.
From what I can tell, those are the key features that people tend to opine about. So, if that is the case, I suspect that TESV will push graphics and story so that it wins over the Morrowind and Oblivion fans... they will likely just do away with politics (making me very sad) but that isn't just the trend, but we have enough politics in our faces every day all day constantly and being where they are physically located near our capital, I can see them getting a little tired of it too. They want to escape it as much as we do too (though I must say that I love TES politics and find that fairly escapist).
I don't know, I intern at a studio in D.C. and they always have CNN on. They're usually laughing at it.
Anyway, I think the rift between the Morrowind and Daggerfall fans was that Morrowind was a totally different type of game from Daggerfall and Arena. Whereas Daggerfall was really an enhancement on Arena's style, Morrowind was built from the ground up, and totally unexpected.
Oblivion, on the other hand, addressed and attempted to solve most of the complaints made on the forums, while on the other hand, completely left out most of the stuff that made Morrowind great to begin with.
So, either TESV will be a completely new and cool and surprising concept, built from the ground up, or it will be the complete inverse of Oblivion. No scaled monsters or artifacts, just overpowered monsters everywhere that drop overpowered, unique objects. Absolutely no daedric armor, anywhere. No way to travel, at all, not even by walking. Every bandit is named, but there's like two of them. You can sell stolen items to everyone, even their owner. Magic doesn't regenerate, ever, not even when you sleep or level or use a magicka potion.
Anyway, if it's the latter, the people who are new to the game will love it. The Oblivion fans will be outraged. And the Morrowind fans will just give up. If it's the former, I'll love it and everyone else will hate it.