Today Gazillion Entertainment unveiled their new upcoming Marvel MMO game called Super Hero Squad Online. Not much information has been released about the game but its trailer is scheduled to be debut tomorrow. Check their official site for updates here http://www.shsonline.com/.
No release date announced for the game as of yet. Gazillion Gargantuan studio is also developing another Marvel MMO game called Marvel Universe. This game is being led by former Blizzard North and Diablo series developer.