There's talk of an AMD-developed processor that will be offically revealed and expanded upon at Microsoft's BUILD 2013 conference that's happening in June. However, the launch line-up could be revealed on May 21st, right before E3, or they could split the reveal. Kinect will again be a big part of the system, sporting a brand new sensor system.
Finally, it's been suggested that the regular model will cost around $499 USD, with a subsidized package available that's similar to the $99 Xbox 360 contract.
Whatever comes out of this console, let's just hope it's not actually called the Xbox 720.