Update - 5/21/2013 1:08 PM
It looks like Edge-Online was wrong after all. The new Xbox is called "Xbox One."
According to some leaked footage from the next-gen version of Call of Duty: Ghosts, the Xbox 720 will simply be called "Xbox" and its tagline will be "A new generation begins." The screenshots leaked about 25 minutes before the scheduled Xbox 720 reveal over Twitter from @edgeonline so we shouldn't have to wait very long to confirm whether or not the moniker is official.
To refresh, the possibilities for the official Xbox 720 name include "Xbox Infinity", "Xbox Fusion" and simply "Xbox" has been floated around as well. "Xbox Infinity" looked to be thrown out of the running last week when a Redditor came out as the author of a "leaked" promotional image that went viral, showing an Xbox Infinity logo along with the tagline "Infinite entertainment. Infinite possibilities." Previous comments had questioned the image's authenticity as the text appeared to be slightly slanted, but the image continued to be disseminated.
Following the Redditor's revelation, "Xbox Fusion" seemed the most likely name, particularly after Microsoft purchased a bevy of Fusion-releated URL's such as XboxFusion.com and XboxFusion.de. Now, it looks like the name might simply be "Xbox."
The new leaked screenshot definitely looks like an official Microsoft image and comes from a pretty trusted source –– Edge-Online. Adding to its credence is another leaked screenshot from Call of Duty: Ghosts. It's unclear whether the leaked Call of Duty screenshot comes from gameplay footage or a cutaway scene, but we'd be fairly surprised if it turned out not to be authentic.
At any rate, the Xbox 720 reveal is in sheer minutes, so hit this link to find out if "Xbox" will indeed be the official name.