I'm not too happy about him being the main antagonist in this game, not at all. He's always been the most evil out of all the Daedric Princes in my view.
As the prince of ...forced intercourse and lots of other vile things, I don't think they'll do justice to his scary image at all, what with the game being all cartoony and so far with lots of retcons. There isn't even blood in TESO.
I'm getting a feeling they'll make him behave like Mehrunes Dagon the second and try to conquer Tamriel through violence and whatnot, yet I feel this is so out of character for him.
I think they'll end up ruining Molag Bal.
Another thing, Vivec and Molag Bal have a long history together, I'm suprised they said he won't play a big part in the main quest of the game.
Almalexia will take his place, really?