Durango, will have much better speech detection, according to sources at the Verge. That includes natural language detection, which will allow the Xbox to process normal speech patterns, similar to Apple's Siri. So, for example, instead of saying "Xbox, play 3," you might simply say, "Xbox, where can I watch The X-Files?"
Furthermore, users may be able to turn the new Xbox on using only voice. Speech-to-text is also a possibility, which would allow users to, say, compose Xbox Live messages using only voice. The Verge also mentions a possible function that would allow the Kinect to detect the number of people in a room and suggest suitable multiplayer games (hopefully not used games).
An improved Kinect, possibly bundled with or built into the next Xbox, has been expected for quite some time now. As such, it's not much of a stretch to assume the upgraded device would feature improved voice recognition in addition to improved physical recognition.