I know it would never happen because Microsoft would refuse to sell at a loss, but let's just break it down really simply.
PS4 is substantially more powerful than Xbox One.
PS4 costs $399.
Xbox One costs $499.
A $100 price cut would not even suffice because in my world of logic, having the PS4 and Xbox One at the same price would make no sense because the PS4 is a more powerful console, it should be more expensive. That's how electronics work. An Nvidia GTX 780 is more expensive than a GTX 480 because it's more powerful.
Bottom line, Xbox One should be the same price as the Wii U. Wii U has the excuse for being so expensive because of the tablet controller and backwards compatibility. Everyone knows Wii U is selling at a profit and Nintendo doesn't sell at a loss. I don't believe that Kinect costs as much as that tablet controller.
After seeing what the Xbox One is capable of and the specs under the hood, it's a $299 console. In a couple years, it should be $199.