Id like a mass effect mmo, that could be pretty big. that universe has a lot of potential and is widely known through the single player games. but instead of making 8 stories like tor just have a smaller number and make the quality of the stories better.
I have it on good authority that depending on how successful TOR is, will determine if Bioware is going to go that exact route.
Ok, A few things I need to address here before making my prediction:
Firstly, Marvel Universe will have NO character customisation, apparently, the player will choose one of the main lore characters (Hulk, Spiderman etc) nd be stuck like that, Marvel even said they will restrict each hero to one user, meaning that the servers will be severely limited in population capacity.
Secondly, Transformers Universe will be in a deathmatch-style format (an exampole would be World of Tanks), and I am sorry, but I do not think such an MMO willbe the next big thing, the more WoW-style RPG format is obviously far more popular, so MMos using a WoT format do not really count imho.
Now, my prediction for the next big game is going to be one that suprisingly, no-one has mentioned. Warhammer 40,000: Dark Millenium Online. This is going to be an action MMORPG using the same combat system as the recent Space Marine game (which had an amazing combat system). If this is a proper RPG like WoW (which it is said to be) then this will be my favourite MMO of all time.
Plus, assault bikes...freaking assault bikes! Give me assault bikes now! If DMO has proper vehicle accelaration, "raids" being tied to quests and other such things, I will be a very happy man, but I would still be ecstatic for a "WoW-clone" with a 40K look (ironic considering Starcraft was "inspired" by 40K).