Although it's not changing the focus of the product, Microsoft has changed the code name for the version of Windows that will follow Windows Vista from Blackcomb to Vienna. However, the final product won't be called Windows Vienna.
The Vienna code name marks a return to city code names. In the past, Microsoft used such code names as Cairo, Chicago, and Detroit for its Windows products. A Microsoft spokesperson noted that the company's new code-name strategy for OS products is to use names for "the kinds of places we all want to see \[and\] experience and that capture the imagination. Vienna fits with this concept." So did Blackcomb, although it's a picturesque ski resort in British Columbia, not a major city.
My guess is that Microsoft wanted to divorce itself from a code name that, because it followed Vista's "Longhorn," was associated with constant delays. Although Microsoft never made any concrete promises for Blackcomb's release, Blackcomb and Longhorn are linked--if Longhorn is delayed, then Blackcomb is delayed. And if Longhorn loses features, as it has, then presumably those features will appear in Blackcomb, as each upcoming Windows version tends to become a dumping ground for features that don't make the current product version.
Microsoft has promised to accelerate the development of future Windows versions in the wake of the Vista fiasco, so one might expect Vienna to arrive more quickly than its predecessor. Also, according to the company's product road map, Vienna will be a minor update, not a major release like Vista.