Vista is a huge and costly flop for Microsoft, they only sold 300 million copies this year, and barely 200 million copies of Office 2007, and IE is barely 80% of the browser market at this rate they will be out of business any second now. They might as well turn off the lights and go home.
However if they can hold on just long enough to release Windows 7 in 2010 then it might postpone their timely demise by a couple years at best.