I think business users generate more money. And business users want the desktop.
The registry hack and required specs (minimum resolution for Metro apps) show that the traditional start menu will be included in the final product. How easily one will be able to switch back and forth remains to be seen.
It's easy to lose sight of the fact that the developers in WinDiv are Windows users too. I think they'll understand that some people will absolutely have to have the traditional start menu and know that the immersive start menu won't cater to everyone, especially those without touch screens.