The Dark Forces Team are teasing on their forum a new build of Windows Phone 7 with number 8750, which is believed to be the Tango branch of the operating system.
They have released the screen shot to the left, which, if genuine, suggests that Tango will continue to be marketed as Windows Phone 7.5.
Tango is meant to expand the addressable market of Windows Phone 7 with support for more languages and geographies and lower price points.
According to previously leaked road maps we can expect to see devices running the OS by the middle of the year, and it is widely expected that Microsoft will be talking about the OS at Mobile World Congress which starts on February 27th.
Of course there is no way to know if the screen shot is not simply faked, and so far, besides teasing the build number, no more information was forthcoming on the DFT forum.
Feel free however to have a sniff around in the 15 pages of the topic here.