Epic Games has confirmed that they are developing a brand new IP.  Epic Games lead animator Jay Hosfelt confirmed the news during the "Animation Bootcamp: Animation Prototyping for Games," which Polygon attended.

No details, platforms or release dates were mentioned.  However, Hosfelt did reveal that Epic is developing the game without a publishing partner.  This means that the game, whatever it is, won't be exclusive to a single platform like Gears of War was.

A model was shown off that looked eerily similar to the Unreal Engine 3 "Samaritan" Tech Demo.  Epic's Paul Meegan took to Twitter to confirm that the game has nothing to do with the demo.  "We love that people are excited about our unannounced game, but it's entirely new and has nothing to do with the Samaritan demo."

Additionally, PR manager Wes Phillips commented to Polygon that what was shown during the presentation was not representative of the actual unannounced project.  "The visuals in Jay’s GDC talk represent sample content we give to Unreal Engine 4 licensees. And even though he talked about our prototyping process, there were no visuals in his presentation that represent our unannounced game."

Hopefully we'll figure out what Epic Games brand new IP is soon.