Starting with version 14, the product we all know and love as "XBMC," will become "Kodi," a new name with new art and branding that the developers say more appropriately fits the media center's promise, as opposed to its long-established roots.
The XBMC-er, Kodi Team explained that part of the name change was because "Xbox Media Center" is long outdated compared to what the software can do today. They noted that it barely runs on the Xbox at all anymore, and they wanted to shed "media center" for "entertainment center" since some of the best features aren't just for local media—you can play games, stream from the web, connect to your mobile devices, and more. They also mentioned that the name had some legal issues—because "Xbox" was in the name, they had no real legal control over "XBMC," which led to a number of copycats and confusing products not affiliated with their work but using their name.
For the end user though, the changes are really in name and branding only. The software will stay the same, the code licensing is still GPL 2.0, and they're not even changing the numbering scheme (the new version will still be v. 14). It's just a new name and a new look for a product we all know and love.