X-bit Labs reports a leaked roadmap refers to Microsoft's next-gen Xbox as "Loop":
After Microsoft decided to go on with rather strange Xbox 360 name for its second generation Xbox game console, many wondered what would be the name of the third-generation. According to a Microsoft roadmap published unofficially, the Xbox Next will carry "Loop" name (or it may be a code-name) and will be, as already revealed, become available in 2013.
The Microsoft roadmap, which includes both software and hardware, published by MS nerd blog claims that the software giant will announce Xbox "loop" at the E3 show in June '13 and will launch it at Build conference in September, 2013. Given the fact that the release of the console depends not only on the readiness of software and hardware, but also the ability to manufacture such hardware in volume, any dates two years ahead of the release should be considered as preliminary.