Microsoft has registered a number of various domains including XboxFusion.com (XboxFusion.biz, XboxFusion.de, XboxFusion.co.uk, etc) that all redirect to the official English Xbox website. Although these dormins where apparently registered back in February they were recently uncovered by Fusible. They also list the rumored names, along site possible domains, that Microsoft owns.
With the next Xbox announcement coming on May 21 having an unknown name carries a lot of weight to it. Perhaps the next Xbox won’t be the Xbox 720 but the Xbox Fusion.