And this isn't just tabs, but wp8's kernel too.
The Windows 8 Consumer Preview—notably it's not being called a "beta"—will be launched on February 29th. Microsoft will launch it at an event it's hosting in Barcelona to coincide with Mobile World Congress.
Taking full advantage of the opportunity afforded by the leap year, the release will just hit Microsoft's previously announced "late February" date. Redmond has no comment (yet) on whether the event will be Webcast.
Releasing the Consumer Preview of a desktop operating system at a conference for cellular communications might seem strange. But with Windows 8's tablet ambitions and the leaked information that Windows Phone 8 will probably use the Windows 8 kernel, this is a desktop operating system that won't be confined to the desktop.