After Sony revealing that they are planning the PS4 and Nintendo are obviously developing the Wii 2, its not really a surprise that Microsoft have also said they are working on the next Xbox too.
Although the Xbox 720 is a obvious new name for the next console, they have said that this is only a "Pet Name" and might not be the final console.
Its a long article but Microsofts plans are that they plan to annouce the new Xbox at E3 2012 or near abouts.
well to be honest the original xbox was like OMG!, i have a xbox 360 but its not setup, i dont plan to set it up, i have my ps3 and my pc. But i also will buy the next one, but i dont think 720 is a good name, and i hope its not the name because i thought 360 was because you can put on any side, but should be 90 and is can only go on two sides