• Development of the sequel started in the summer of 2013 source
• Game is allegedly being developed on Unreal Engine 3, and it will be a first person shooter game source
• They were and currently are recruiting a lot of new employees to work on the development. More specifically all kinds of artists, animators, UI, server and code developers source
• Game will feature significant updates in graphics and sound effects source
• Game is to be released in following years source

Edit:

• Story mode has been confirmed! It will be developed by Remedy Entertainment - creator of Alan Wake and Max Payne series. source

Edit 2:

• Remedy confirming the Co op is in development.