Gameloft is working on quite an amount of great games recently, and Dead Rivals is one of it. It will be a zombie-themed action MMORPG (which I believe it is inspired by Left 4 Dead).
There are 2 different playable characters shooting over different types of zombies (that huge fat guy looks alike with Boomer in L4D) in the trailer. The game is in third-person view, apparently you can shoot automatically too. According to the description under the official trailer, the game will have an open world. Character are customizable, you can also build shelters, craft weapons and develop character skills.
For now, no launch date is confirmed yet. These are all we know, stay tuned for updates!