Many of us think that by the time Windows 9 or 10 arrives the desktop would disappear. But according to the following MSDN blog, Microsoft considers desktop important and intends to keep desktop for the foreseeable future :
"We believe in the Windows desktop. It powers the experiences today that make a Windows 7 PC the most popular device in the world. So, even if we believe that over time many scenarios will be well-served by Metro style apps, for the foreseeable future, the desktop is going to continue to play a key role in many people’s lives. So we are going to improve it. We’re having a good dialog about what folks might think about our design choices but also wanted to put these choices in a broader context of the unmatched utility of the desktop."
Designing for Metro style and the desktop - Building Windows 8 - Site Home - MSDN Blogs