That purported road map comes courtesy of WMPoweruser, which included a screen cap of it in a Dec. 27 posting. The blog also declined to mention its source for the information, which (at least in broad strokes) jibes with past data from other places.
Supposedly, the second quarter of 2012 will see the arrival of a "Tango" update, which according to the road map's handy bullet points will feature "products with the best prices." This likely means Windows Phones aimed at the midmarket, with a possible stripped-down user interface to match the lower cost.
In the fourth quarter of that year would come "Apollo," aimed at both the "superphone" (i.e., higher-end specifications) and "business" categories. A road map bullet point also suggests "increase overall volume," which could mean Microsoft anticipates more Windows Phone units in users' hands by the end of 2012, or else it is hoping that smartphones loaded with some sort of Apollo software update will kick off a higher volume of sales.
Despite the Microsoft brand name and phones from several manufacturers, Windows Phone failed to gain much traction with consumers in 2011. During his July 11 keynote speech at Microsoft's Worldwide Partner Conference, CEO Steve Ballmer described Windows Phone's market presence as "very small."
Tango and Apollo rumors have floated for some time. Back in August, Mary-Jo Foley posted on her All About Microsoft blog that she'd heard of "two Tango releases on tap," with the first aiming to expand "the Windows Phone footprint into new markets" while the second "will be targeted at low-cost devices and include fixes and new features."
Meanwhile, Apollo had already been tagged (by Slashgear and other sources) as Microsoft's next big code update. However, possible features remain unclear. In any case, if this road map is accurate, it shows that Microsoft has robust update plans to accompany a hard Windows Phone push by Nokia and some other manufacturers.