There has been a lot of speculation about the name of the console that will succeed the Xbox 360. We know the code name is "Durango," but that's just an internal development name--the Xbox 360 carried the code name "Xenon." New domain name registrations and redirects now provide convincing evidence that Microsoft will market the new Xbox under the brand name "Xbox Fusion." See also: Microsoft launches Xbox One - as it happened, details.
Many have simply called Microsoft's next console the Xbox 720, because that's twice 360, right? But of course that wouldn't be the official name, because it's sort of dumb. More recently, a convincing mock-up from Reddit user C-Ron had the rumor mill convinced that the name of the next Xbox would be Xbox Infinity. That's not a bad name at all, but it's not necessarily real.
Recently, domain name registrations related to the name "Xbox Fusion" sprang up. Microsoft owns the domains for XboxFusion.com, XboxFusion.co.uk, XboxFusion.biz, and several others. Perhaps more important, each of those domains currently redirects to the official Xbox page, which is currently dominated by an ad inviting you to tune in on Tuesday, May 21 at 10am pacific time for the reveal of the next-generation Xbox. Microsoft does not own domains related to Xbox 720, Xbox Infinity, or other popular potential Xbox names. The company does own domains like Xbox8.us and XboxLiveTV.com, and has for years, but those seem to be held as a defensive maneuver, not for immediate use. Those domains just direct to Bing searches, not to the official Xbox site.
None of this is an official announcement, nor is it ironclad proof that "Xbox Fusion" is really the name of the next box. It could all be a red herring, or Microsoft covering its bases. But frankly, this is as close to a confirmation of the new name as you're likely to get before Tuesday. If Xbox Fusion isn't the name of the next Xbox, it's almost certainly the name of a major feature or service.