That was rendered on a I5/I7 rig with (3) Nvidia 580's SLI'd with 4xMSAA on if I recallc orrectly..
That was footage of a demo powered by the previously released Unreal 3 engine.
They also stated they were able to get comparable images on with significantly lower antialiasing requirements on the NVIDIA's new Kepler GPU. This in no way means that the new Kepler has the processing power of (3) 580's in SLI.
They have not publically demonstrated the capabilities of Unreal 4 engine yet. They have privately behind closed doors with strict Non disclosure agreements.
We will have to wait until we have a finished product featuring the Unreal 4 engine and driver optimization occurrs to see how Nvidia and AMD's different GPU families stack up against each other.
Right now all we can do is speculate what it will take to run this.